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As filed with the U.S. Securities and Exchange Commission on September 30, 2026.

Registration No. 333-             

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

FORM S-4

REGISTRATION STATEMENT
UNDER

THE SECURITIES ACT OF 1933

Spark I Acquisition Corporation*
(Exact name of registrant as specified in its charter)

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For co-registrants, see “Table of Co-Registrants” on the following page.

3790 El Camino Real

Unit #570

Palo Alto, CA 94306

(650) 353-7082
(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Bernard Moon
Secretary

3790 El Camino Real
Unit #570

Palo Alto, CA 94306
(650) 353-7082

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

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Approximate date of commencement of proposed sale to the public: As soon as practicable after (i) this registration statement is declared effective and (ii) upon completion of the applicable transactions described in the enclosed proxy statement/prospectus.

If the securities being registered on this Form are being offered in connection with the formation of a holding company and there is compliance with General Instruction G, check the following box: ☐

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering: ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering: ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

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If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ☐

If applicable, place an X in the box to designate the appropriate rule provision relied upon in conducting this transaction:

Exchange Act Rule 13e-4(i) (Cross-Border Issuer Tender Offer) ☐

Exchange Act Rule 14d-1(d) (Cross-Border Third-Party Tender Offer) ☐

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The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until the registration statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

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TABLE OF CO-REGISTRANTS

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ZincFive, Inc.
20050 SW 112th Ave
Tualatin, Oregon 97062
Tel: (503) 399-3517

Tod Higinbotham
Chief Executive Officer
ZincFive, Inc.
20050 SW 112th Ave
Tualatin, Oregon 97062
Tel: (503) 399-3517

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PRELIMINARY PROXY STATEMENT — SUBJECT TO COMPLETION DATED SEPTEMBER 30, 2026

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PROXY STATEMENT FOR EXTRAORDINARY GENERAL MEETING OF

SPARK I ACQUISITION CORPORATION

(A CAYMAN ISLANDS EXEMPTED COMPANY)

AND

PROSPECTUS FOR        SHARES OF COMMON STOCK

AND

WARRANTS TO PURCHASE SHARES OF COMMON STOCK OF

SPARK I ACQUISITION CORPORATION

(TO BE RENAMED “ZINCFIVE, INC.” FOLLOWING DOMESTICATION IN

THE STATE OF DELAWARE AND IN CONNECTION WITH THE BUSINESS COMBINATION DESCRIBED IN THIS PROXY STATEMENT/PROSPECTUS)

In connection with the Domestication and in accordance with the Plan of Domestication, attached to this proxy statement/prospectus as Annex B: (i) each Class A ordinary share of SPKL, par value $0.0001 per share (the “SPKL Class A Ordinary Share”) issued and outstanding immediately prior to the Domestication will remain outstanding and will automatically convert, on a one-for-one basis, into one share of common stock of ZincFive, par value $0.0001 per share (the “ZincFive Common Stock”); (ii) each Public Warrant (as defined below) and Private Placement Warrant (as defined below), each exercisable for one SPKL Class A Ordinary Share at an exercise price of $11.50 per share, subject to adjustment (the “SPKL Warrant”), will be automatically converted into one share of redeemable warrant exercisable for one share of ZincFive Common Stock (the “ZincFive Warrant”) on the same terms as the SPKL Warrants; and (iii) each unit sold in the IPO, each consisting of one SPKL Class A Ordinary Share and one-half of one Public Warrant (the “SPKL Unit”), issued and outstanding will automatically be cancelled and each holder thereof will be entitled, per SPKL Unit, to one share of ZincFive Common Stock and one-half of one ZincFive Warrant. No fractional ZincFive Warrants will be issued in the process described in this clause (iii).

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In connection with the Domestication and subject to the satisfaction or waiver of the conditions set forth in the Merger Agreement, including approval of the Condition Precedent Proposals (as defined elsewhere in this proxy statement/prospectus) by SPKL’s shareholders: (i) the governing documents of SPKL will be replaced by the Proposed Certificate of Incorporation and the Proposed Bylaws (the “Proposed Organizational Documents”), attached to this proxy statement/prospectus as Annex C and Annex D, respectively, and (ii) SPKL will be renamed “ZincFive, Inc.”

At Closing, pursuant to the terms of the Merger Agreement:

Legacy ZincFive will take all actions necessary or appropriate so that, immediately prior to the Closing, all shares of Legacy ZincFive Preferred Stock (other than Legacy ZincFive Series F Stock) will be converted into shares of Legacy ZincFive Common Stock (the “Conversion”) pursuant to the terms of the Merger Agreement. See the section entitled “Description of ZincFive’s Securities” for more information regarding the ZincFive Common Stock. Following the Conversion, no shares of Legacy ZincFive Preferred Stock (other than Legacy ZincFive Series F Stock) will be outstanding and each holder of Legacy ZincFive Preferred Stock (other than Legacy ZincFive Series F Stock) will thereafter cease to have any rights with respect to any shares of Legacy ZincFive Preferred Stock.

Concurrently with the execution of the Merger Agreement, SPKL entered into the Sponsor Agreement, dated June 11, 2026, with SLG SPAC Fund LLC, a Delaware limited liability company (the “Sponsor”), SPKL, certain stockholders of the SPKL and Legacy ZincFive (as amended by the Amendment to Sponsor Agreement, dated September 28, 2026, the “Sponsor Agreement”), pursuant to which the Sponsor agreed to, among other things: (i) vote in favor of adoption of the SPKL Stockholder Matters; (ii) vote against any Acquisition Transaction (as defined in the Merger Agreement) and any merger agreement or merger other than the Merger Agreement and the Business Combination; and (iii) convert all outstanding SPKL Class B Ordinary Shares held by the Sponsor into SPKL Class A Ordinary Shares immediately prior to the Domestication. In addition, the Sponsor separately agreed to forfeit, immediately following the Closing, (i) 3,500,000 shares of ZincFive Common Stock to be issued to Alyeska Master Fund, L.P. (the “Lead Purchaser”) as a condition to the Lead Purchaser’s participation in the Series A Preferred Investment; (ii) 922,078 shares of ZincFive Common Stock to be issued to the investors (the “First Tranche Bridge Investors”) who provided bridge financing to Legacy ZincFive in the form of secured promissory notes (the “Bridge Notes”) pursuant to the Note Purchase Agreement, dated April 23,

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2026, by and among Legacy ZincFive and the investor parties thereto (the “Bridge Investors”) before the public announcement of the Business Combination and 1,458,400 ZincFive Warrants to be issued to certain of the Bridge Investors; and (iii) 2,786,867 ZincFive Warrants and 50% of any ZincFive Warrants issued as a result of the conversion of $1,500,000 of the unpaid principal balance of the Convertible Note (as defined below) into Working Capital Warrants (as defined below) to be reserved for issuance as stock options under the ZincFive, Inc. 2026 Equity Incentive Plan (the “2026 Plan”).

Pursuant to the Proposed Bylaws of ZincFive to be in effect at the First Effective Time, and subject to certain exceptions, stockholders of ZincFive will not be permitted to, from the Closing Date until the earlier of 11:59 p.m., New York time, on (x) the date that is the later of one hundred eighty (180) days after the date that a registration statement (the “Resale Registration Statement”) covering the resale of Registrable Securities (as defined in the A&R Registration Rights Agreement) initially becomes effective and          days after the Closing Date, or, in the case of affiliates of ZincFive as of the Closing Date, twelve (12) months after the date the Resale Registration Statement becomes effective, and (y) the date on which ZincFive completes a liquidation, merger, stock exchange or other similar transaction that results in all of its stockholders having the right to exchange their shares of ZincFive Common Stock for cash, securities or other property, (i) exchange, transfer, assign, lend, sell, offer to sell, contract or agree to sell, hypothecate, pledge, grant any option to purchase or otherwise dispose of or agree to dispose of, directly or indirectly, or establish or increase a put equivalent position or liquidate or decrease a call equivalent position within the meaning of Section 16 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and the rules and regulations of the U.S. Securities and Exchange Commission (the “SEC”) promulgated thereunder with respect to, any shares of ZincFive Common Stock (A) issued as consideration pursuant to the Merger Agreement held by any such holders as of the Closing, (B) issued upon the settlement or exercise of options, restricted stock units or other equity awards or warrants outstanding as of immediately prior to the Closing that are assumed by ZincFive held by any such holders as of the Closing, (C) issued to employees of ZincFive, or (D) otherwise held by Sponsor, the officers and directors of Sponsor or ZincFive, or its and their respective affiliates as of the Closing (such shares, the “Lock-Up Shares”; provided that shares of ZincFive Common Stock issued pursuant to the ZincFive, Inc. 2026 Employee Stock Purchase Plan (the “ESPP”) will not constitute Lock-Up Shares), (ii) enter into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of any Lock-Up Shares, whether any such transaction is to be settled by delivery of such securities, in cash or otherwise, or (iii) publicly announce any intention to effect any transaction specified in clause (i) or (ii).

The Proposed Bylaws provide for certain customary permitted transfers, including transfers to certain affiliates, members, partners, family members, or for estate planning purposes. Further, if the volume- weighted average price (“VWAP”) of ZincFive Common Stock equals or exceeds $12.00 for twenty (20) trading days within any period of thirty (30) consecutive trading days commencing at least one hundred eighty (180) days after the date the Resale Registration Statement becomes effective, then the transfer restrictions applicable to the Lock-Up Shares will expire. Notwithstanding the foregoing, the board of directors of ZincFive (the “ZincFive Board”) may grant a discretionary waiver or termination of the lockup restrictions. Any such discretionary waiver or termination shall apply to each other holder of Lock-Up Shares in the same proportion that the number of Lock-Up Shares held by the holder of Lock-Up Shares with respect to which such lockup restrictions are being terminated or waived bears to the total number of Lock-Up Shares then held by such holder (a “Pro-Rata Release”). A Pro-Rata Release shall not apply or be required in the case of an early release from the lockup restrictions if such early release is made (i) with respect to a number of shares of ZincFive Common Stock equal to $2,500 for each holder of Lock-Up Shares, calculated as of the Closing Date, rounded up to the nearest share, to the extent that a holder of such shares is not an affiliate of SPKL or ZincFive; (ii) solely for the purposes of complying with certain initial and continued listing requirements of Nasdaq or to comply with ZincFive’s obligations under the Series A Securities Purchase Agreement; or (iii) due to circumstances of an emergency or hardship, each as determined by the ZincFive Board or any duly authorized committee thereof in its sole judgment.

Prior to the Closing, Legacy ZincFive intends to enter into lockup agreements with each Legacy ZincFive stockholder that holds 1% or more of the outstanding Legacy ZincFive Common Stock. The lockup agreements are expected to provide for a restriction on transfers of Lock-Up Shares for up to twelve (12) months after the date the Resale Registration Statement becomes effective and otherwise on substantially identical terms as the lockup restrictions contained in the Proposed Bylaws that are applicable to affiliates of ZincFive as of the Closing Date.

Concurrently with the execution of the Merger Agreement, on June 11, 2026, SPKL and Legacy ZincFive entered into the Series A Securities Purchase Agreement (the “Series A Securities Purchase Agreement”) with certain institutional and accredited investors (the “Series A Preferred Investors”). Pursuant to the Series A Securities Purchase Agreement, the Series A Preferred Investors have agreed to purchase, concurrently with the Closing, an aggregate of 10,441,174 shares of the 12.0% Series A Cumulative Convertible Preferred Stock of ZincFive, par value $0.0001 per share (the “Series A Preferred Stock”), having the rights, preferences and privileges set forth in the Certificate of Designation of Preferences, Rights and Limitations of 12.0% Series A

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Cumulative Convertible Preferred Stock (the “Certificate of Designation”) and warrants to purchase a number of shares of ZincFive Common Stock equal to the number of shares into which such shares of ZincFive Common Stock underlying such investor’s Series A Preferred Stock are initially convertible (the “Series A Preferred Investor Warrants”), for an aggregate purchase price of $106.5 million (the “Series A Preferred Investment”). Certain Series A Preferred Investors will satisfy their purchase price obligations through the cancellation of their Bridge Notes in exchange for shares of Series A Preferred Stock and Series A Preferred Investor Warrants. The consummation of the Series A Preferred Investment is conditioned upon the satisfaction or waiver of certain customary closing conditions, including the Available Closing SPAC Cash (as defined in the Merger Agreement) being not less than $100,000,000 at the Closing.

The following table illustrates the pro forma ownership in ZincFive immediately following the consummation of the Business Combination, under each of: (i) the No Redemption Scenario and (ii) the Maximum Redemption Scenario, each as defined below and excluding the dilutive effect of: (a) the Private Placement Warrants (as defined below); (b) the Public Warrants (as defined below); (c) the Working Capital Warrants into which the Convertible Note (as defined below) can be converted; and (d) the Series A Preferred Investor Warrants:

For more information, please see the sections of this proxy statement/prospectus entitled “Unaudited Pro Forma Condensed Combined Financial Information” and “Beneficial Ownership of Securities.”

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The Memorandum and Articles of Association provide that SPKL must complete its initial business combination by March 29, 2027, or such earlier date as the SPKL Board may approve, or such later date as the shareholders of SPKL may approve in accordance with the Memorandum and Articles of Association (the “Combination Period”). If SPKL is unable to complete the Business Combination or another initial business combination by such date, SPKL will: (i) cease all operations except for the purpose of winding up; (ii) as promptly as reasonably possible but not more than ten business days thereafter, redeem the Public Shares, at a per-share price, payable in cash, equal to the aggregate amount then on deposit in the trust account of SPKL (the “Trust Account”), including interest earned on the funds held in the Trust Account (less taxes payable and up to $100,000 of interest to pay dissolution expenses), divided by the number of the then-outstanding Public Shares, which redemption will completely extinguish rights of Public Shareholders (as defined below) as shareholders (including the right to receive further liquidation distributions, if any); and (iii) as promptly as reasonably possible following such redemption, subject to the approval of SPKL’s remaining shareholders and the SPKL Board, liquidate and dissolve, subject in the case of clauses (ii) and (iii) to SPKL’s obligations under Cayman Islands law to provide for claims of creditors and the requirements of other applicable law. The Sponsor and SPKL’s officers and directors have entered into an agreement with SPKL, pursuant to which they have waived their rights to liquidating distributions from the Trust Account with respect to their Founder Shares if SPKL fails to consummate an initial business combination within the Combination Period.

The SPKL Units, SPKL Class A Ordinary Shares and Public Warrants are currently listed on The Nasdaq Stock Market LLC (“Nasdaq”) under the symbols “SPKLU,” “SPKL” and “SPKLW,” respectively. Pursuant to the terms of the Merger Agreement, SPKL is required to cause the ZincFive Common Stock issued in the Domestication to be approved for listing on the NYSE, Nasdaq, or such other stock exchange as mutually agreed to by SPKL and Legacy ZincFive (the “Stock Exchange”). There can be no assurance that such listing condition will be met. If the listing condition is not met, the Business Combination will not be consummated unless the listing condition is waived by the parties to the Merger Agreement. Following the Closing, ZincFive Common Stock and ZincFive Warrants will be listed, subject to the approval of the Stock Exchange, under the proposed symbols “ZFIV” and “ZFIVW,” respectively. We may not have received confirmation from a Stock Exchange of approval of the listing of the ZincFive Common Stock and ZincFive Warrants at the time of the Extraordinary General Meeting or prior to the Closing. The listing condition to the Closing may be waived by the parties to the Merger Agreement. As a result, you may be asked to vote to approve the Business Combination and the other proposals included in this proxy statement/prospectus without such confirmation. Further, it is possible that such confirmation may never be received, and the Business Combination could still be consummated if such condition is waived. In such event, the ZincFive Common Stock and ZincFive Warrants may not be listed on any Stock Exchange.

Material Financing Transactions of SPKL

Prior to the IPO, the Sponsor paid $25,000, or approximately $0.004 per share, to cover certain expenses on our behalf in consideration of 6,870,130 Class B ordinary shares of SPKL, par value $0.0001 per share (“SPKL Class B Ordinary Shares”, together with the SPKL Class A Ordinary Shares, “SPKL Ordinary Shares”, and such SPKL Class B Ordinary Shares initially issued to the Sponsor, the “Founder Shares”), and on April 1, 2022, the Sponsor sold and transferred a total of 850,000 Founder Shares to certain of SPKL’s officers and directors, at a purchase price equal to the par value per share. Up to 448,052 Founder Shares were subject to forfeiture by the Sponsor depending on the extent to which the underwriter’s over-allotment option was exercised, and, pursuant to that certain letter agreement, dated as of October 5, 2023, by and among SPKL, the Sponsor and the members of SPKL’s board of directors and management team party thereto (the “Letter Agreement”), and up to 3,435,065 Founder Shares were subject to forfeiture if the Forward Purchaser (as defined in the Letter Agreement) exercises its right to terminate or reduce its commitment to purchase forward purchase securities pursuant to that certain forward purchase agreement, dated as of October 5, 2023, by and between SPKL and SparkLabs Group Management, LLC (the “Forward Purchase Agreement”) or in the event of SPKL’s liquidation and subsequent dissolution. On October 10, 2023, at the request of SPKL, Cantor Fitzgerald & Co. (“Cantor”) informed SPKL that it would not be exercising the over-allotment option. As a result, the Sponsor forfeited an aggregate of 448,052 Founder Shares, and such forfeited shares were cancelled by SPKL prior to the consummation of the IPO. Additionally, pursuant to the Sponsor Agreement, the Letter Agreement was amended to provide that the Sponsor will not be obligated to surrender any Founder Shares (or any SPKL Class A Ordinary Share issued upon conversion thereof) as a result of the Forward Purchaser not fulfilling its commitment under the Forward Purchase Agreement. Accordingly, no forfeiture of Founder Shares as contemplated under the Letter Agreement will occur in connection with the Business Combination regardless of whether the Forward Purchaser fulfills its commitment.

Since the IPO, the following material financing transactions have occurred or will occur in connection with the consummation of the Business Combination: (i) simultaneously with the consummation of the IPO, the Sponsor purchased an aggregate of 8,490,535 warrants, each exercisable to purchase one SPKL Class A Ordinary Share, or, following the Domestication, one share of ZincFive Common Stock, at an exercise price of $11.50 per share (the “Private Placement Warrants”), at a price of $1.00 per warrant in a private placement, generating total proceeds of $8,490,535; (ii) on January 28, 2025, SPKL issued a convertible unsecured promissory

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note (the “Convertible Note”) in the principal amount of up to $1,900,000 to the Sponsor, of which $1,900,000 is outstanding, which does not bear interest and is repayable upon the consummation of the Business Combination, with the Sponsor having the option to convert up to $1,500,000 of the outstanding principal balance into warrants with terms identical to the Private Placement Warrants (the “Working Capital Warrants”), at a price of $1.00 per warrant upon consummation of the Business Combination; (iii) on June 25, 2025, SPKL issued a non-convertible unsecured promissory note (the “Non-Convertible Note”) in the principal amount of up to $2,500,000 to the Sponsor, of which $     was outstanding as of     , 2026, which does not bear interest and is repayable upon the earlier of the consummation of the Business Combination and the last day that SPKL has to complete a business combination; (iv) following the approval of a proposal to amend the Memorandum and Articles of Association to extend the date by which we have to consummate an initial business combination from July 11, 2025 to September 29, 2026 (the “First Extension”) at the extraordinary general meeting of SPKL’s shareholders held on July 8, 2025 (the “First Extension Meeting”), SPKL committed to make monthly deposits (the “First Extension Contributions”) into the Trust Account in an amount equal to the lesser of (A) $0.015 for each outstanding SPKL Class A Ordinary Share and (B) $55,000, up to a maximum aggregate amount of $825,000, to extend SPKL’s time period to consummate a business combination from July 11, 2025 to September 29, 2026; (v) following the approval of a proposal to amend the Memorandum and Articles of Association to extend the date by which we have to consummate an initial business combination from September 29, 2026 to March 29, 2027 (the “Second Extension”) at the extraordinary general meeting of SPKL’s shareholders held on September 25, 2026 (the “Second Extension Meeting”), SPKL committed to make monthly deposits (the “Second Extension Contributions” and together with the First Extension Contributions, the “Contributions”) into the Trust Account in an amount equal to $0.015 for each outstanding SPKL Class A Ordinary Share, up to a maximum aggregate amount of $201,304, to extend SPKL’s time period to consummate a business combination from September 29, 2026 to March 29, 2027, with aggregate deposits of $          having been made into the Trust Account through             , 2026; and (vi) the Series A Preferred Investment. The Non-Convertible Note, which includes the aggregate amount of the Contributions deposited into the Trust Account, and $of the Convertible Note will be repaid upon the consummation of the Business Combination, except that, with respect to the Convertible Note, up to $1,500,000 of the outstanding principal balance may be converted at the Sponsor’s option into Working Capital Warrants with terms identical to the Private Placement Warrants at a price of $1.00 per warrant, pursuant to the Sponsor Agreement.

Sponsor Compensation

The Sponsor currently holds 4,000,000 SPKL Class A Ordinary Shares and 1,572,078 SPKL Class B Ordinary Shares. The compensation and securities received or to be received by the Sponsor in connection with the Business Combination and related transactions upon the consummation of the Business Combination is: (i)            1,150,000 shares of ZincFive Common Stock issuable upon a one-for-one conversion of all of the SPKL Ordinary Shares held by Sponsor, with an implied aggregate market value of $   million (based upon the closing price of SPKL Class A Ordinary Shares of $       on Nasdaq on                     , 2026, the most recent practicable date prior to the date of this proxy statement/prospectus), which reflects the forfeiture of (a) 3,500,000 shares to be issued to the Lead Purchaser and (b) 922,078 shares to be issued to the First Tranche Bridge Investors, each pursuant to the Sponsor Agreement; (ii) 4,245,268 ZincFive Warrants, issuable upon a one-for-one conversion of all of the Private Placement Warrants held by the Sponsor, with an implied aggregate market value of $   million (based upon the closing price of the Public Warrants, each exercisable for one SPKL Class A Ordinary Share or, following the Domestication, one share of ZincFive Common Stock, at an exercise price of $11.50 (the “Public Warrants”), of $       on Nasdaq on, 2026, the most recent practicable date prior to the date of this proxy statement/prospectus), which reflects the forfeiture of (a) 2,786,867 ZincFive Warrants to be reserved for issuance as stock options under the 2026 Plan and (b) 1,458,400 ZincFive Warrants to be issued to certain of the Bridge Investors, each pursuant to the Sponsor Agreement; (iii) 750,000 ZincFive Warrants issuable upon a one-for- one conversion of all of the Working Capital Warrants to be held by the Sponsor, assuming full conversion of $1,500,000 of the unpaid principal balance of the Convertible Note into Working Capital Warrants, of which $        million is outstanding as of , 2026, the most recent practicable date prior to the date of this proxy statement/prospectus, which ZincFive Warrants would have an implied aggregate market value of $          million (based upon the closing price of the Public Warrants of $          on Nasdaq on           , 2026, the most recent practicable date prior to the date of this proxy statement/prospectus), which reflects the forfeiture of 50% of such warrants to be reserved for issuance as stock options under the 2026 Plan pursuant to the Sponsor Agreement; (iv) $          representing repayment of the remainder of the outstanding balance of the Convertible Note; (v) $          representing repayment of the Non-Convertible Note, of which $          million is outstanding, which includes an aggregate of $           in Contributions deposited into the Trust Account; and (vi) $           representing reimbursement of out-of-pocket expenses incurred by the Sponsor in connection with identifying, investigating and completing an initial business combination, as further described below, each as of           , 2026, the most recent practicable date prior to the date of this proxy statement/prospectus. In no event will the Sponsor or any of SPKL’s existing officers or directors or any of their respective affiliates be paid any finder’s fee, consulting fee or other compensation prior to, or for any services rendered to effectuate, the completion of the Business Combination, other than the fees, and reimbursement of out-of-pocket expenses described herein.

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Set forth below is a summary of the price paid and the amount of compensation and securities received or to be received by the Sponsor in connection with the Business Combination and related transactions:

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Currently, holders of the SPKL Class A Ordinary Shares sold in the IPO (the “Public Shareholders” and such shares, the “Public Shares”) hold     SPKL Class A Ordinary Shares subject to possible redemption. To the extent that the Sponsor elects to receive the repayment of the Convertible Note in Working Capital Warrants and subsequently exercises such warrants to acquire ZincFive Common Stock, the resulting issuances of ZincFive Common Stock may result in material dilution of the non-redeeming Public Shareholders.

Further detail regarding the compensation and securities received or to be received by the Sponsor and its affiliates, and the extent of any potential dilution that may be caused thereby to the non-redeeming holders of SPKL Class A Ordinary Shares, is provided in the sections of this proxy statement/prospectus entitled “Questions and Answers for Shareholders of SPKL — What equity stake will current SPKL shareholders and Legacy ZincFive Securityholders hold in ZincFive immediately after the Closing?” and “Summary of the Proxy Statement/Prospectus — The Proposals to be Submitted at the Extraordinary General Meeting — The Business Combination Proposal — Dilution.”

In no event will the Sponsor or any of SPKL’s existing officers or directors or any of their respective affiliates, be paid any finder’s fee, consulting fee or other compensation in connection with the Business Combination or related transactions. However, SPKL’s officers and certain directors are entitled to compensation in the form of consulting fees in connection with consulting and board services as described in “Information About SPKL.” SPKL also pays an affiliate of the Sponsor a total of $1,000 per month for office space, telecommunication services, security, utilities, maintenance, and other administrative services. In addition, the Sponsor and SPKL’s officers and directors, or their respective affiliates, are entitled to reimbursement for any out-of-pocket expenses related to identifying, investigating and completing an initial business combination. In addition, the Sponsor is entitled to reimbursement for transaction expenses advanced and/or paid by the Sponsor on behalf of SPKL or Legacy ZincFive. As of           , 2026, the most recent practicable date prior to the date of this proxy statement/prospectus, the Sponsor and SPKL’s officers and directors are awaiting reimbursement for $                 of such expenses which would be reimbursed at Closing.

This proxy statement/prospectus covers: (i)          shares of ZincFive Common Stock (including shares that are to be issued or may be issuable upon the conversion of SPKL Ordinary Shares into ZincFive Common Stock), which number is based on the assumptions set forth in the section of this proxy statement/ prospectus entitled “Frequently Used Terms — Share Calculations and Ownership Percentages”; and (ii) ZincFive Warrants.

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SPKL will hold an extraordinary general meeting to consider matters relating to the Business Combination at      , Eastern Time, on           , 2026, electronically at     (the “Extraordinary General Meeting”). There is no requirement to attend the Extraordinary General Meeting in person. You or your proxyholder will be able to attend and vote at the Extraordinary General Meeting in-person or online by visiting and using a control number assigned by Continental Stock Transfer & Trust Company, SPKL’s transfer agent. To register and receive access to the Extraordinary General Meeting, registered shareholders and beneficial shareholders (those holding shares through a stock brokerage account or by a bank or other holder of record) will need to follow the instructions applicable to them provided in this proxy statement/prospectus.

After careful consideration, the SPKL Board has unanimously approved the Merger Agreement and the other proposals described in this proxy statement/prospectus. The SPKL Board has also determined that it is advisable to consummate the Business Combination and that the Business Combination is in the best interests of the Public Shareholders. The SPKL Board took into account the oral opinion of Houlihan Capital, LLC (“Houlihan Capital”) (subsequently confirmed in writing), rendered on June 10, 2026, to the effect that, as of such date and based upon and subject to the procedures followed, assumptions made, qualifications and limitations on the review undertaken, and other matters considered by Houlihan Capital in preparing its opinion, the Business Combination and related transactions are fair, from a financial point of view, to the unaffiliated shareholders of SPKL. A copy of the written opinion is attached as Annex M to this proxy statement/prospectus. Please see the section entitled “The Business Combination Proposal — Fairness Opinion of Houlihan Capital, LLC” for further information. The SPKL Board recommends that you vote “FOR” each proposal described in this proxy statement/prospectus.

If you have any questions or need assistance voting your SPKL Ordinary Shares, please contact Advantage Proxy, Inc., the proxy solicitor for SPKL, by calling 877-870-8565 (toll-free), or banks and brokers can call 206-870-8565, or by emailing ksmith@advantageproxy.com.

The notice of the Extraordinary General Meeting and this proxy statement/prospectus will be available at.

This proxy statement/prospectus provides shareholders of SPKL with detailed information about the Business Combination and other matters to be considered at the Extraordinary General Meeting. We encourage you to read this entire document, including the annexes and other documents referred to in this proxy statement/ prospectus, carefully and in their entirety. It also contains or references information about SPKL, Legacy ZincFive and ZincFive and certain related matters. In particular, when you consider the recommendation regarding the proposals by the SPKL Board, you should keep in mind that the Sponsor and certain of SPKL’s directors and officers have interests in the Business Combination that may be different from, or in addition to, your interests as a shareholder, and there may be actual or potential material conflicts of interest between or among (i) the Sponsor, SPKL, SPKL’s officers and directors, and Legacy ZincFive’s officers and directors and (ii) unaffiliated security holders of SPKL. Such conflicts of interest may include a material conflict of interest arising in determining whether to proceed with the Business Combination and the compensation of the Sponsor in connection with the Business Combination. For instance, the Sponsor and certain of SPKL’s officers and directors will benefit from the completion of an initial business combination and may be incentivized to complete an acquisition of a less favorable target company or on terms less favorable to shareholders rather than liquidating the Trust Account. Legacy ZincFive’s directors and executive officers have interests in the Business Combination that are different from, or in addition to, those of the SPKL shareholders generally. See the sections of this proxy statement/prospectus entitled “The Business Combination Proposal — Certain Interests of SPKL’s Directors and Officers and Others in the Business Combination” and “The Business Combination Proposal – Certain Interests of Legacy ZincFive’s Directors and Officers in the Business Combination” for a further discussion of these considerations. You should also carefully consider the risk factors described under the heading “Risk Factors” beginning on page 65 of this proxy statement/prospectus.

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES REGULATORY AGENCY HAS APPROVED OR DISAPPROVED THE TRANSACTIONS DESCRIBED IN THIS PROXY STATEMENT/PROSPECTUS, PASSED UPON THE MERITS OR FAIRNESS OF

THE BUSINESS COMBINATION OR PASSED UPON THE ADEQUACY OR ACCURACY OF THE DISCLOSURE IN THIS PROXY STATEMENT/PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY CONSTITUTES A CRIMINAL OFFENSE.

This proxy statement/prospectus is dated            , 2026, and is first being mailed to SPKL’s shareholders on or about      , 2026.

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SPARK I ACQUISITION CORPORATION

A Cayman Islands Exempted Company

3790 El Camino Real, Unit #570

Palo Alto, CA 94306

NOTICE OF EXTRAORDINARY GENERAL MEETING TO BE HELD ON           , 2026

TO THE SHAREHOLDERS OF SPARK I ACQUISITION CORPORATION:

NOTICE IS GIVEN that an extraordinary general meeting (including any adjournments or postponements of the extraordinary general meeting, the “Extraordinary General Meeting”) of Spark I Acquisition Corporation, a Cayman Islands exempted company with limited liability (“SPKL”), will be held on         2026, at              , Eastern Time, electronically at            .

The Extraordinary General Meeting will be held for the following purposes:

Proposal No. 1 — The Business Combination Proposal — To consider and vote upon a proposal to approve by ordinary resolution, and adopt the Merger Agreement, dated as of June 11, 2026, attached to the accompanying proxy statement/prospectus as Annex A (as amended, supplemented or otherwise modified from time to time in accordance with its terms, the “Merger Agreement”), by and among SPKL, Spark I Acquisition Corporation Sub I Inc., a Delaware corporation (“Merger Sub I”), Spark I Acquisition Corporation Sub II LLC, a Delaware limited liability company (“Merger Sub II”), and ZincFive, Inc., a Delaware corporation (“Legacy ZincFive”), pursuant to which, at the closing of the transactions contemplated by the Merger Agreement (the “Closing”) and at least one day following the Domestication (as defined below), Merger Sub I will merge with and into Legacy ZincFive (the “First Merger”), with Legacy ZincFive continuing as the surviving corporation (the “Surviving Corporation”), and, immediately following the First Merger, Legacy ZincFive, as the Surviving Corporation, will merge with and into Merger Sub II (the “Second Merger” and, together with the First Merger, the “Mergers”), with Merger Sub II continuing as the surviving entity and a direct wholly owned subsidiary of ZincFive (as defined below). The transactions contemplated by the Merger Agreement are described in more detail in the accompanying proxy statement/prospectus and are referred to as the “Business Combination.” We refer to this proposal as the “Business Combination Proposal.”

Proposal No. 2 — The Domestication Proposal — To consider and vote upon a proposal to approve, by special resolution, and adopt the plan of domestication (as may be amended, supplemented or otherwise modified from time to time in accordance with its terms, the “Plan of Domestication”) attached to the accompanying proxy statement/prospectus as Annex B, and a change in the corporate domicile of SPKL, which will be accomplished by way of deregistering SPKL as an exempted company registered under the laws of the Cayman Islands with limited liability and registering SPKL by way of continuation and domestication as a corporation under the laws of the State of Delaware in accordance with the Plan of Domestication (the “Domestication”). The Domestication will be effected in accordance with the Plan of Domestication at least one day prior to the Closing by SPKL filing a certificate of corporate domestication and the proposed new certificate of incorporation of ZincFive, as the post-Business Combination company (the “Proposed Certificate of Incorporation”) with the Secretary of State of the State of Delaware and filing an application to deregister with the Registrar of Companies in the Cayman Islands. Upon the effectiveness of the Domestication, SPKL will continue as a Delaware corporation and under the corporate name “ZincFive, Inc.” (“ZincFive”). All outstanding securities of SPKL will become outstanding securities of ZincFive, as described in more detail in the accompanying proxy statement/prospectus. We refer to this proposal as the “Domestication Proposal.”

Proposal No. 3 — The Stock Issuance Proposal — To consider and vote upon a proposal to approve, by ordinary resolution, for purposes of complying with the applicable provisions of Nasdaq Listing Rule 5635, the issuance (or reservation for issuance) of: (i) shares of ZincFive Common Stock to the Legacy ZincFive Securityholders in connection with the Business Combination; (ii) shares of 12.0% Series A Cumulative Convertible Preferred Stock of ZincFive (the “Series A Preferred Stock”) and warrants to purchase a number of shares of ZincFive Common Stock equal to the number of shares into which such shares of ZincFive Common Stock underlying Series A Preferred Stock held by Series A Preferred Investors (as defined herein) are initially convertible (the “Series A Preferred Investor Warrants”) pursuant to that certain Series A Securities Purchase Agreement (the “Series A Securities Purchase Agreement”), dated as of June 11, 2026, by and among SPKL, Legacy ZincFive and the other purchasers identified on the signature pages thereto (the “Series A Preferred Investors”); (iii) shares of ZincFive Common Stock issuable upon conversion of Series A Preferred Stock and upon exercise of Series A Preferred Investor Warrants; (iv) shares of ZincFive Common Stock to the Lead Purchaser and certain Series A Preferred Investors pursuant to the Sponsor Agreement; and (v) any other preferred stock, common stock and securities convertible into or exercisable for common stock

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pursuant to subscription, purchase or similar agreements that SPKL has entered, or may enter, into prior to the Closing. We refer to this proposal as the “Stock Issuance Proposal.”

Proposal No. 4 — The Organizational Documents Proposal — To consider and vote upon a proposal to approve, by special resolution, the Proposed Certificate of Incorporation and the Proposed Bylaws of ZincFive, as the post-Business Combination company (the “Proposed Bylaws” and, together with the Proposed Certificate of Incorporation, the “Proposed Organizational Documents”) in connection with the Domestication. We refer to this proposal as the “Organizational Documents Proposal.” The form of each of the Proposed Certificate of Incorporation and the Proposed Bylaws is attached to the accompanying proxy statement/prospectus as Annex C and Annex D, respectively.

Proposal No. 5 — The Advisory Organizational Documents Proposals — To consider and vote upon the following five separate proposals (collectively, the “Advisory Organizational Documents Proposals”) to approve on an advisory non-binding basis and in accordance with applicable U.S. Securities and Exchange Commission (the “SEC”) guidance, by ordinary resolution, each of the following material differences between SPKL’s amended and restated memorandum and articles of association (the “Memorandum and Articles of Association”) and the Proposed Organizational Documents:

Proposal No. 6 — The Incentive Plan Proposal — To consider and vote upon a proposal to approve by ordinary resolution, the ZincFive, Inc. 2026 Equity Incentive Plan (the “2026 Plan”). A form of the 2026 Plan is attached to the accompanying proxy statement/prospectus as Annex H. We refer to this proposal as the “Incentive Plan Proposal.”

Proposal No. 7 — The Employee Stock Purchase Plan Proposal — To consider and vote upon a proposal to approve by ordinary resolution, the ZincFive, Inc. 2026 Employee Stock Purchase Plan (the “ESPP”). A form of the ESPP is attached to the accompanying proxy statement/prospectus as Annex I. We refer to this proposal as the “Employee Stock Purchase Plan Proposal.”

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Proposal No. 8 — The Director Election Proposal — To consider and vote upon a proposal to approve by ordinary resolution the election of directors to serve on the ZincFive Board, each until such director’s successor is duly elected and qualified or until such director’s earlier death, resignation or removal. We refer to this proposal as the “Director Election Proposal,” and, collectively with the Business Combination Proposal, the Domestication Proposal, the Stock Issuance Proposal, the Organizational Documents Proposal, the Incentive Plan Proposal and the Employee Stock Purchase Plan Proposal, the “Condition Precedent Proposals.”

Proposal No. 9 — The Adjournment Proposal — To consider and vote upon a proposal to approve by ordinary resolution, the adjournment of the Extraordinary General Meeting to a later date or dates, if necessary: (i) to permit further solicitation and vote of proxies in the event that there are insufficient votes for the approval of one or more proposals at the Extraordinary General Meeting; (ii) for the absence of a quorum; (iii) to allow reasonable additional time for the filing or mailing of any supplemental or amended disclosure that SPKL has determined in good faith after consultation with outside legal counsel is required under applicable law and for such supplemental or amended disclosure to be disseminated and reviewed by its shareholders prior to the Extraordinary General Meeting; or (iv) to engage with investors. We refer to this proposal as the “Adjournment Proposal.”

These items of business are described in the accompanying proxy statement/prospectus, which we encourage you to read carefully and in its entirety before voting.

Only holders of record of Class A ordinary shares, par value $0.0001 per share (“SPKL Class A Ordinary Shares”), and Class B ordinary shares, par value $0.0001 per share, of SPKL (“SPKL Class B Ordinary Shares” and, together with the SPKL Class A Ordinary Shares, “SPKL Ordinary Shares”), including those held by SPKL’s sponsor, SLG SPAC Fund LLC, a Delaware limited liability company (the “Sponsor”), at the close of business on    , 2026 (the “Record Date”) are entitled to notice of and to have their votes counted at the Extraordinary General Meeting.

The approval of each of the Domestication Proposal and the Organizational Documents Proposal requires a special resolution under the Companies Act (As Revised) of the Cayman Islands and the Memorandum and Articles of Association. A special resolution requires the affirmative vote of at least two-thirds of the votes cast by the holders of the issued SPKL Ordinary Shares, voting together as a single class, who are present in person, virtually or represented by proxy and entitled to vote. In regard to the Domestication Proposal, pursuant to Article 182 of the Memorandum and Articles of Association,holders of SPKL Class B Ordinary Shares will have ten votes for every SPKL Class B Ordinary Share and holders of SPKL Class A Ordinary Shares will have one vote for every SPKL Class A Ordinary Share.

The approval of each of the Business Combination Proposal, the Stock Issuance Proposal, the Advisory Organizational Documents Proposals, the Incentive Plan Proposal, the Employee Stock Purchase Plan Proposal, the Director Election Proposal and the Adjournment Proposal requires an ordinary resolution, being the affirmative vote of at least a majority of the votes cast by the holders of the issued SPKL Ordinary Shares, who are present in person, virtually or represented by proxy and entitled to vote on the respective proposal at the Extraordinary General Meeting. In regard to the Director Election Proposal, pursuant to Article 96 of the Memorandum and Articles of Association, the approval of the Director Election Proposal requires an ordinary resolution of the holders of the SPKL Class B Ordinary Shares only, being the affirmative vote of at least a simple majority of the votes cast by the holders of the issued SPKL Class B Ordinary Shares, who are present in person, virtually or represented by proxy and entitled to vote at the Extraordinary General Meeting. As of the date of this proxy statement/prospectus, the Sponsor has agreed, and SPKL’s officers and directors intend, to vote the SPKL Class B Ordinary Shares owned by them in favor of the Director Election Proposal. As of the Record Date, the Sponsor and SPKL Insiders own all of the issued and outstanding SPKL Class B Ordinary Shares. As a result, approval of the Director Election Proposal will not require the affirmative vote of shareholders other than the vote of the Sponsor and the SPKL Insiders.

The accompanying proxy statement/prospectus and proxy card are being provided to SPKL’s shareholders in connection with the solicitation of proxies to be voted at the Extraordinary General Meeting. Whether or not you plan to attend the Extraordinary General Meeting, all of SPKL’s shareholders are urged to read the accompanying proxy statement/prospectus, including the annexes and the documents referred to in the accompanying proxy statement/prospectus, carefully and in their entirety. You should also carefully consider the risk factors described under the heading “Risk Factors” beginning on page 65 of the accompanying proxy statement/prospectus.

After careful consideration, the board of directors of SPKL (the “SPKL Board”) has unanimously approved the Business Combination and unanimously recommends that shareholders vote “FOR” the adoption of the Merger Agreement and approval of the transactions contemplated thereby, including the Domestication and the Business Combination, and “FOR” all other proposals

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presented to SPKL’s shareholders in the accompanying proxy statement/prospectus. When you consider the recommendation of these proposals by the SPKL Board, you should keep in mind that the Sponsor and certain of SPKL’s directors and officers have interests in the Business Combination that may be different from, or in addition to, your interests as a shareholder, and there may be actual or potential material conflicts of interest between or among (i) the Sponsor, SPKL’s officers and directors, and Legacy ZincFive’s officers and directors and (ii) unaffiliated security holders of SPKL. Such conflicts of interest may include a material conflict of interest arising in determining whether to proceed with the Business Combination and the compensation of the Sponsor in connection with the Business Combination. For instance, the Sponsor and certain of SPKL’s officers and directors will benefit from the completion of an initial business combination and may be incentivized to complete an acquisition of a less favorable target company or on terms less favorable to shareholders rather than liquidating the Trust Account. Legacy ZincFive’s directors and executive officers have interests in the Business Combination that are different from, or in addition to, those of the SPKL shareholders generally. For instance, the Sponsor and certain of SPKL’s officers and directors will benefit from the completion of a business combination and may be incentivized to complete an acquisition of a less favorable target company or on terms less favorable to shareholders rather than liquidating SPKL. See the sections of the accompanying proxy statement/prospectus entitled “The Business Combination Proposal — Certain Interests of SPKL’s Directors and Officers and Others in the Business Combination” and “The Business Combination Proposal — Certain Interests of Legacy ZincFive’s Directors and Officers in the Business Combination” for a further discussion of these considerations.

In connection with the Business Combination, certain related agreements have been or will be entered into at or prior to the Closing, including the A&R Registration Rights Agreement and the Sponsor Agreement (each term as defined in the accompanying proxy statement/prospectus). See “The Business Combination Proposal — Certain Agreements Related to the Business Combination” and “Certain Relationships and Related Party Transactions” in the accompanying proxy statement/prospectus for more information.

Pursuant to the Memorandum and Articles of Association, a holder of SPKL Class A Ordinary Shares issued as part of the units (“SPKL Units”) issued in our initial public offering (“IPO”), whether purchased in our IPO or following our IPO in the open market (a “Public Shareholder,” and such shares, “Public Shares”), may request to redeem all or a portion of such holder’s Public Shares for cash if the Business Combination is consummated. As a holder of Public Shares, you will be entitled to receive cash for any Public Shares to be redeemed only if you:

Holders must complete the procedures for electing to redeem their Public Shares in the manner described above prior to 5:00 p.m., Eastern Time, on            , 2026 (two business days before the initially scheduled date of the Extraordinary General Meeting) for their Public Shares to be redeemed (the “Redemption Deadline”).

The address of the Transfer Agent is listed under the question “Questions and Answers for Shareholders of SPKL — Who can help answer my questions?” of this proxy statement/prospectus.

Public Shareholders will be entitled to request that their Public Shares be redeemed for an amount equal to each Public Share’s pro rata portion of the aggregate amount then on deposit in the Trust Account in accordance with the Memorandum and Articles of Association (the “Redemption Price”). For illustrative purposes, as of           , 2026, this would have amounted to approximately $      per issued and outstanding Public Share. However, the proceeds deposited in the Trust Account could become subject to the claims of SPKL’s creditors, if any, which could have priority over the claims of the Public Shareholders. The per share distribution from the Trust Account in such a situation may be less than originally expected due to such claims. Whether you vote, and if you do vote, how you vote, on any proposal, including the Business Combination Proposal, will have no impact on the amount you will receive upon exercise of your redemption rights. The redemption of Public Shares will be effected while SPKL remains a Cayman Islands exempted company, prior to the Domestication, and it is expected that the Redemption Price will be paid to Public Shareholders electing to redeem their Public Shares promptly after the Closing.

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Any request for redemption, once made by a holder of Public Shares, may not be withdrawn following the Redemption Deadline, unless the SPKL Board determines (in its sole discretion) to permit such withdrawal of a redemption request (which it may do in whole or in part). Furthermore, if a holder of a Public Share delivers its share certificates (if any) along with the redemption forms in connection with an election of its redemption and subsequently decides prior to the Redemption Deadline not to elect to exercise such rights, it may simply request that SPKL permit the withdrawal of the request for redemption and instruct the Transfer Agent, to return the share certificates (physically or electronically). The holder can make such request by contacting the Transfer Agent at the address or email address listed in this proxy statement/ prospectus.

Any corrected or changed written exercise of redemption rights must be received by the Transfer Agent at least two business days prior to the initially scheduled date of the Extraordinary General Meeting. No request for redemption will be honored unless the holder’s certificates for Public Shares (if any) along with the redemption forms have been delivered (either physically or electronically) to the Transfer Agent, at least two business days prior to the initially scheduled date of the Extraordinary General Meeting.

If a holder of Public Shares properly makes a request for redemption and the certificates for Public Shares (if any) along with the redemption forms are delivered as described above, then, if the Business Combination is approved, SPKL will effect the redemption of such Public Shares while SPKL remains a Cayman Islands exempted company, and pay the Redemption Price, calculated as of two business days prior to the Closing, promptly following the Closing. If the Business Combination is not consummated, the Public Shares will be returned to the respective holder, broker or bank.

If you are a holder of Public Shares and you exercise your redemption rights, such exercise will not result in the loss of any Public Warrants that you may hold.

See the section of the accompanying proxy statement/prospectus entitled “Extraordinary General Meeting of SPKL — Redemption Rights” for a detailed description of the procedures to be followed if you wish to redeem your Public Shares.

Notwithstanding the foregoing, a Public Shareholder, together with any affiliate of such Public Shareholder or any other person with whom such Public Shareholder is acting in concert or as a “group” (as defined in Section 13(d)(3) of the Securities Exchange Act of 1934, as amended), will be restricted from redeeming its Public Shares with respect to more than an aggregate of 15% of the Public Shares sold in our IPO. Accordingly, if a Public Shareholder, alone or acting in concert or as a group, seeks to redeem more than 15% of the Public Shares sold in our IPO, then any such shares in excess of that 15% limit would not be redeemed for cash.

The Sponsor and each director and officer of SPKL who holds shares of SPKL have agreed to vote in favor of the Business Combination, and to waive their redemption rights in connection with the Closing with respect to any SPKL Ordinary Shares held by them. None of the Sponsor, directors or officers received separate consideration for their waiver of redemption rights. Further, concurrently with the execution of the Merger Agreement, the Sponsor entered into a Sponsor Agreement, dated June 11, 2026, with SPKL, Legacy ZincFive and certain shareholders of SPKL (as amended by the Amendment to Sponsor Agreement, dated September 28, 2026, the “Sponsor Agreement”). Pursuant to the terms and conditions of the Sponsor Agreement, the Sponsor agreed to, among other things, vote its SPKL Ordinary Shares in favor of each Shareholder Proposal (as defined in the accompanying proxy statement/ prospectus) being presented at the Extraordinary General Meeting. The SPKL Ordinary Shares held by the Sponsor will be excluded from the pro rata calculation used to determine the per-share Redemption Price. As of the Record Date, the Sponsor owns approximately             % of the issued and outstanding SPKL Ordinary Shares.

The consummation of the Business Combination is conditioned upon the satisfaction or written waiver (where permissible) by the parties to the Merger Agreement of certain customary closing conditions. These conditions include: (i) the adoption or approval, as applicable, by SPKL’s shareholders of: (A) the Merger Agreement and the Business Combination in accordance with applicable law and exchange rules and regulations; (B) the Domestication; (C) the Proposed Certificate of Incorporation and the Proposed Bylaws; (D) approval of the issuance of shares of ZincFive Common Stock as required by the listing rules of the applicable stock exchange; (E) the adoption by SPKL of the 2026 Plan and the ESPP; (F) the election of members of the ZincFive Board (in the form of an advisory vote, with the directors being elected by written resolution of the holders of the SPKL Class B Ordinary Shares in accordance with the SPKL’s organizational documents); (G) the amendment of SPKL’s organizational documents, effective immediately prior to the Closing, to remove references to the $5,000,001 net tangible assets requirements set forth in SPKL’s organizational documents; (H) any other proposals as the SEC (or staff members of the SEC) may indicate are necessary in its comments to the proxy statement included in this proxy statement/prospectus or any related correspondence; (I) any proposals the parties to the Merger Agreement agree are necessary or desirable to consummate the Business Combination, and (J) adjournment of the special meeting, if necessary, to permit further solicitation of the proxies because there are not sufficient votes to approve and adopt any of the foregoing; (ii) the

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receipt of the requisite consent of the stockholders of Legacy ZincFive; (iii) any applicable waiting period or any extension of any applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976 (and the rules and regulations promulgated under such Act) in respect of the Business Combination being expired or earlier terminated without the imposition of burdensome conditions; (iv) the Registration Statement becoming effective; (v) SPKL having filed with the applicable stock exchange an application or supplemental listing application for the listing of the ZincFive Common Stock, and such shares of ZincFive Common Stock having been approved for listing, subject to official notice of issuance; (vi) the accuracy of the representations and warranties of each of the parties to the Merger Agreement and the performance of the covenants and agreements of such parties subject, in each case, to customary standards; (vii) the completion of the Domestication; (viii) the Available Closing SPAC Cash (as defined in the Merger Agreement) not being less than $100,000,000; and (ix) approval by the SPKL shareholders to extend the time SPKL has to consummate an initial business combination pursuant to the terms of the SPKL organizational documents. For more information, see the section of this proxy statement/ prospectus entitled “The Business Combination Proposal — Merger Agreement — Conditions to Closing — General Conditions.”

The SPKL Units, SPKL Class A Ordinary Shares and Public Warrants are currently listed on The Nasdaq Stock Market LLC under the symbols “SPKLU,” “SPKL” and “SPKLW,” respectively. Pursuant to the terms of the Merger Agreement, SPKL is required to cause the ZincFive Common Stock issued in the Domestication to be approved for listing on the NYSE, Nasdaq, or such other stock exchange as mutually agreed to by SPKL and Legacy ZincFive (the “Stock Exchange”). There can be no assurance that such listing condition will be met. If the listing condition is not met, the Business Combination will not be consummated unless the listing condition is waived by the parties to the Merger Agreement. Following the Closing, ZincFive Common Stock and ZincFive Warrants will be listed, subject to the approval of the Stock Exchange, under the proposed symbols “ZFIV” and “ZFIVW,” respectively. We may not have received confirmation from a Stock Exchange of approval of the listing of the ZincFive Common Stock and ZincFive Warrants at the time of the Extraordinary General Meeting or prior to the Closing. The listing condition to the Closing may be waived by the parties to the Merger Agreement. As a result, you may be asked to vote to approve the Business Combination and the other proposals included in the accompanying proxy statement/ prospectus without such confirmation. Further, it is possible that such confirmation may never be received, and the Business Combination could still be consummated if such condition is waived. In such event, the ZincFive Common Stock and ZincFive Warrants may not be listed on any Stock Exchange.

Your vote is very important. Whether or not you plan to attend the Extraordinary General Meeting, please vote as soon as possible by following the instructions in the accompanying proxy statement/ prospectus to make sure that your shares are represented at the Extraordinary General Meeting. If you hold your shares in “street name” through a bank, broker or other nominee, you will need to follow the instructions provided to you by your bank, broker or other nominee to ensure that your shares are represented and voted at the Extraordinary General Meeting. The transactions contemplated by the Merger Agreement will be consummated only if the Condition Precedent Proposals are approved at the Extraordinary General Meeting, and if the other conditions to closing are satisfied or waived. Each of the Condition Precedent Proposals is cross-conditioned on the approval of each other Condition Precedent Proposal. The Advisory Organizational Documents Proposals are conditioned on the approval of each of the Condition Precedent Proposals. The Adjournment Proposal is not conditioned upon the approval of any other proposal set forth in the accompanying proxy statement/prospectus.

If you sign, date and return your proxy card without indicating how you wish to vote, your proxy will be voted “FOR” each of the proposals presented at the Extraordinary General Meeting. If you fail to return your proxy card or fail to instruct your bank, broker or other nominee how to vote, and do not attend the Extraordinary General Meeting in person or virtually, the effect will be, among other things, that your shares will not be counted for purposes of determining whether a quorum is present at the Extraordinary General Meeting and will not be voted. If you are a shareholder of record and you attend the Extraordinary General Meeting and wish to vote in person or virtually, you may withdraw your proxy and vote in person or virtually.

TO EXERCISE YOUR REDEMPTION RIGHTS, YOU MUST SUBMIT A WRITTEN REQUEST, INCLUDING THE LEGAL NAME, PHONE NUMBER AND ADDRESS OF THE BENEFICIAL OWNER OF THE SHARES FOR WHICH REDEMPTION IS REQUESTED, TO THE TRANSFER AGENT THAT YOUR PUBLIC SHARES BE REDEEMED FOR CASH. YOU MUST ALSO DELIVER YOUR PUBLIC SHARES TO THE TRANSFER AGENT, PHYSICALLY OR ELECTRONICALLY USING THE DTC’S DWAC (DEPOSIT WITHDRAWAL AT CUSTODIAN) SYSTEM IN ACCORDANCE WITH THE PROCEDURES AND DEADLINES DESCRIBED IN THE ACCOMPANYING PROXY STATEMENT/PROSPECTUS. IF THE BUSINESS COMBINATION IS NOT CONSUMMATED, THEN THE PUBLIC SHARES WILL NOT BE REDEEMED FOR CASH. IF YOU HOLD THE SHARES IN STREET NAME, TO EXERCISE YOUR REDEMPTION RIGHTS YOU MUST INSTRUCT THE ACCOUNT EXECUTIVE AT YOUR BANK OR BROKER TO WITHDRAW THE SHARES FROM YOUR ACCOUNT. SEE THE SECTION OF THE ACCOMPANYING PROXY STATEMENT/PROSPECTUS ENTITLED “EXTRAORDINARY GENERAL MEETING OF SPKL — REDEMPTION RIGHTS” FOR MORE SPECIFIC INSTRUCTIONS.

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On behalf of the SPKL Board, I would like to thank you for your support and look forward to the successful completion of the Business Combination.

Sincerely,

James Rhee

Chief Executive Officer and Chairman of the Board of Directors

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES REGULATORY AGENCY HAS APPROVED OR DISAPPROVED THE TRANSACTIONS DESCRIBED IN THE ACCOMPANYING PROXY STATEMENT/PROSPECTUS, PASSED UPON THE MERITS OR FAIRNESS OF THE BUSINESS COMBINATION OR RELATED TRANSACTIONS OR PASSED UPON THE ADEQUACY OR ACCURACY OF THE DISCLOSURE IN THE ACCOMPANYING PROXY STATEMENT/PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY CONSTITUTES A CRIMINAL OFFENSE.

The accompanying proxy statement/prospectus is dated     , 2026 and is first being mailed to shareholders on or about      , 2026.

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TABLE OF CONTENTS

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ABOUT THIS PROXY STATEMENT/PROSPECTUS

This proxy statement/prospectus relates to an Agreement and Plan of Merger and Reorganization, dated as of June 11, 2026 (as may be amended, supplemented or otherwise modified from time to time in accordance with its terms, the “Merger Agreement”), by and among Spark I Acquisition Corporation, a Cayman Islands exempted company with limited liability (“SPKL”), Spark I Acquisition Corporation Sub I Inc., a Delaware corporation (“Merger Sub I”), Spark I Acquisition Corporation Sub II LLC, a Delaware limited liability company (“Merger Sub II” and together with Merger Sub I, the “Merger Subs”), and ZincFive, Inc., a Delaware corporation (“Legacy ZincFive”), a copy of which is attached to this proxy statement/prospectus as Annex A.

The Merger Agreement, among other things and subject to the terms and conditions contained therein, provides for (i) the transfer of the registration of SPKL by way of a deregistration of SPKL as an exempted company registered under the laws of the Cayman Islands with limited liability and registration by way of continuation and domestication of SPKL (the “Domestication”) into a Delaware corporation under the applicable provisions of the amended and restated memorandum and articles of association of SPKL (as may be amended from time to time, the “Memorandum and Articles of Association”), the Companies Act (As Revised) of the Cayman Islands (the “Companies Act”) and the Delaware General Corporation Law, as amended (the “DGCL”); and (ii) following the Domestication, (a) the merger of Merger Sub I with and into Legacy ZincFive, with Legacy ZincFive continuing as the surviving corporation (the “Surviving Corporation”) in such merger (the “First Merger”), and (b) immediately following the First Merger, the merger of the Surviving Corporation with and into Merger Sub II, with Merger Sub II continuing as the surviving entity (the “Surviving Entity”) in such merger (the “Second Merger” and together with the First Merger, the “Mergers,” and, together with the Domestication and other transactions contemplated by the Merger Agreement, the “Business Combination”). In connection with the Business Combination, SPKL will change its name to “ZincFive, Inc.” We refer to the new public entity following the consummation of the Business Combination as “ZincFive.”

This proxy statement/prospectus serves as:

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REFERENCES TO ADDITIONAL INFORMATION

The proxy statement/prospectus incorporates important business and financial information that is not included in or delivered with this proxy statement/prospectus. This information is available for you to review through the SEC’s website at www.sec.gov.

You may request copies of this proxy statement/prospectus or other information concerning SPKL and Legacy ZincFive, without charge, in writing at Spark I Acquisition Corporation, 3790 El Camino Real, Unit #570, Palo Alto, CA 94306 or by telephone (650) 353-7082; or Advantage Proxy, Inc., the proxy solicitor for SPKL, by calling 877-870-8565 (toll-free), or banks and brokers can call 206-870-8565, or by emailing ksmith@advantageproxy.com, or from the SEC through the SEC website at the address provided above.

To receive timely delivery of the documents in advance of the Extraordinary General Meeting of Spark I Acquisition Corporation to be held on            , 2026, you must request the information no later than five business days prior to the date of the Extraordinary General Meeting, or no later than          , 2026.

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FREQUENTLY USED TERMS

Unless otherwise stated or unless the context otherwise requires, prior to the Business Combination, the terms “we,” “us,” “our,” and “SPKL” refer to SPKL. Following the Business Combination, the terms “we,” “us” and “our” refer to ZincFive and, where appropriate, its subsidiaries. Prior to the Domestication, SPKL is an exempted company incorporated under the laws of the Cayman Islands. Following the Domestication, subject to shareholder approval, SPKL will be a corporation incorporated under the laws of the State of Delaware and will be renamed “ZincFive, Inc.” Following the Domestication, SPKL is referred to in this document as ZincFive.

In this proxy statement/prospectus:

“2026 Plan” means the ZincFive, Inc. 2026 Equity Incentive Plan, which will become effective upon the Closing. A copy of the 2026 Plan is attached to this proxy statement/prospectus as Annex H.

“A&R Registration Rights Agreement” means the Amended and Restated Registration Rights Agreement to be entered into by SPKL, the Sponsor and certain holders of Legacy ZincFive Common Stock and Legacy ZincFive Preferred Stock as of immediately prior the First Effective Time, concurrently with the Closing.

“Adjournment Proposal” means the proposal to be considered at the Extraordinary General Meeting to adjourn the Extraordinary General Meeting to a later date or dates, if necessary, (i) to permit further solicitation of proxies; (ii) for absence of a quorum; (iii) to allow time for supplemental disclosure; or (iv) to engage with investors.

“Advisory Organizational Documents Proposals” means the five proposals to be considered at the Extraordinary General Meeting to approve, on a non-binding advisory basis and as required by applicable SEC guidance, certain material differences between the Memorandum and Articles of Association and the Proposed Organizational Documents.

“Ancillary Documents” means documents ancillary to the Transactions.

“Available Closing SPAC Cash” means the amount calculated in accordance with Section 10.03(d) of the Merger Agreement, consisting of (i) the aggregate cash proceeds released from the Trust Account after giving effect to all redemptions of Public Shares plus (ii) the aggregate net proceeds from the Series A Preferred Investment received at or prior to the Closing, which amount shall not be less than $100,000,000 as a condition to Closing under the Merger Agreement.

“Bridge Investors” means those investors who provided bridge financing to Legacy ZincFive in the form of secured promissory notes (the “Bridge Notes”) in an aggregate principal amount of $34,541,627 in a series of closings commencing on April 23, 2026, pursuant to the Note Purchase Agreement, dated April 23, 2026, by and among Legacy ZincFive and the investor parties thereto.

“Business Combination” means the transactions contemplated by the Merger Agreement.

“Business Combination Proposal” means the proposal to be considered at the Extraordinary General Meeting to approve the Merger Agreement, including the Business Combination described therein.

“Certificate of Designation” means the Certificate of Designation of Preferences, Rights and Limitations of the Series A Preferred Stock. A copy of the form of Certificate of Designation is attached to this proxy statement/prospectus as Annex K.

“Closing” means the closing of the Business Combination. “Closing Date” means the date the Closing occurs.

“Code” means the U.S. Internal Revenue Code of 1986, as amended.

“Combination Period” means the period ending on March 29, 2027 (or such earlier date as the SPKL Board may approve or such later date as the SPKL shareholders may approve in accordance with the Memorandum and Articles of Association), by which SPKL must consummate a Business Combination.

“Companies Act” means the Companies Act (As Revised) of the Cayman Islands.

“Company Support Agreements” means the agreements pursuant to which certain holders of Legacy ZincFive Common Stock and Legacy ZincFive Preferred Stock sufficient to constitute the Company Stockholder Approval have agreed, among other things and

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subject to certain terms and conditions, to vote their respective shares of Legacy ZincFive Common Stock and Legacy ZincFive Preferred Stock in favor of the Merger Agreement, the Mergers and the Transactions. A copy of the form of Company Support Agreement is attached to this proxy statement/prospectus as Annex F.

“Condition Precedent Proposals” means, collectively, the Business Combination Proposal, the Domestication Proposal, the Stock Issuance Proposal, the Organizational Documents Proposal, the Incentive Plan Proposal, the Employee Stock Purchase Plan Proposal, and the Director Election Proposal.

“Contributions” means the First Extension Contributions and the Second Extension Contributions.

“Convertible Note” means the convertible unsecured promissory note, dated January 28, 2025, issued by SPKL to the Sponsor in the principal amount of up to $1,900,000, up to $1,500,000 of which may, at the Sponsor’s election, be converted into Working Capital Warrants.

“Convertible Promissory Note” means those certain convertible promissory notes issued by Legacy ZincFive upon the assignment and assumption of certain existing indebtedness of Legacy ZincFive held by Boxwood Holdings V LLC, an affiliate of SilverBox Corp V, whereby Boxwood Holdings V LLC transferred the debt to such holders, effective upon the execution of the Merger Agreement. The Convertible Promissory Notes bear paid-in-kind interest at 20% per annum and mature two years after issuance with mandatory prepayment on the earlier of (i) the closing of certain business combination transactions or (ii) June 30, 2028. Immediately prior to the consummation of a Business Combination, the principal balance of each note shall automatically be increased to an amount equal to 120% of the principal balance, including paid-in-kind interest.

“Convertible Promissory Noteholders” means the holders of the Convertible Promissory Notes. “DGCL” means Delaware General Corporation Law, as amended.

“Director Election Proposal” means the proposal to be considered at the Extraordinary General Meeting to elect       directors to serve on the ZincFive Board, each until such director’s successors is duly elected and qualified or until such director’s earlier death, resignation or removal.

“Dissenting Shares” means Legacy ZincFive capital stock issued and outstanding immediately prior to the First Effective Time and that are held by stockholders of record or beneficial owners who (i) have not voted in favor of, or consented in writing to, the Mergers, and (ii) have demanded properly in writing appraisal or dissenters’ rights for such Legacy ZincFive capital stock in accordance with Section 262 of the DGCL.

“Domestication” means the deregistration of SPKL as an exempted company registered under the laws of the Cayman Islands with limited liability and registration by way of continuation and domestication of SPKL into a Delaware corporation under the applicable provisions of the Memorandum and Articles of Association, the Companies Act and the DGCL. The term “Domestication” includes all matters and necessary or ancillary changes to effect such domestication, including the adoption of the Proposed Certificate of Incorporation (a form of which is attached to this proxy statement/prospectus as Annex C) consistent with the DGCL and changing the name of the registered agent and the address of the registered office of SPKL.

“Domestication Proposal” means the proposal to be considered at the Extraordinary General Meeting to approve by special resolution the Plan of Domestication and the Domestication.

“DTC” means the Depository Trust Company.

“DWAC” means The Depository Trust Company’s deposit/withdrawal at custodian system.

“Employee Stock Purchase Plan Proposal” means the proposal to be considered at the Extraordinary General Meeting to approve the ESPP.

“ESPP” means the ZincFive, Inc. 2026 Employee Stock Purchase Plan, which will become effective upon the Closing. A copy of the ESPP is attached to this proxy statement/prospectus as Annex I.

“Exchange Act” means the U.S. Securities Exchange Act of 1934, as amended.

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“Exchanged ZincFive Option” means an option to purchase a number of shares of ZincFive Common Stock issued upon the automatic conversion of a Legacy ZincFive Option that is outstanding and unexercised as of immediately prior to the Closing in accordance with the Merger Agreement.

“Exchanged ZincFive RSU” means a restricted stock unit of ZincFive issued upon the automatic conversion of a Legacy ZincFive restricted stock unit that is outstanding and unvested as of immediately prior to the First Effective Time, in accordance with the Merger Agreement.

“Excluded Shares” means Legacy ZincFive capital stock and Legacy ZincFive Preferred Stock held in Legacy ZincFive’s treasury or owned by SPKL, Merger Sub I or Legacy ZincFive immediately prior to the First Effective Time.

“Extraordinary General Meeting” means the extraordinary general meeting of SPKL’s shareholders, to be held at          , Eastern Time, on                         , 2026, electronically at     , and any adjournments or postponements of such extraordinary general meeting.

“First Effective Time” means the date and time that the First Merger becomes effective.

“First Extension” means the proposal to amend our amended and restated memorandum and articles of association to extend the date by which we have to consummate an initial business combination from July 11, 2025 to September 29, 2026.

“First Extension Contributions” means the monthly deposits SPKL committed to make into the Trust Account, following the approval of the First Extension at the First Extension Meeting.

“First Extension Meeting” means the extraordinary general meeting of SPKL’s shareholders held on July 8, 2025.

“First Merger” means the merger of Merger Sub I with and into Legacy ZincFive with Legacy ZincFive continuing as the Surviving Corporation.

“First Tranche Bridge Investors” means those Bridge Investors that purchased Bridge Notes before the public announcement of the Business Combination.

“Forward Purchase Agreement” means that certain forward purchase agreement, dated as of October 5, 2023, by and between SPKL and SparkLabs Group Management, LLC (the “Forward Purchaser”), as may be amended, supplemented or otherwise modified from time to time in accordance with its terms.

“Founder Shares” means the 6,870,130 SPKL Class B Ordinary Shares originally issued to the Sponsor on December 8, 2021, including the 850,000 SPKL Class B Ordinary Shares sold and transferred by the Sponsor to certain of SPKL’s officers and directors on April 1, 2022, at a purchase price equal to the par value per share, in each case as adjusted for any forfeiture, cancellation or conversion thereof, and any SPKL Class A Ordinary Shares issued upon conversion of such SPKL Class B Ordinary Shares.

“GAAP” means U.S. generally accepted accounting principles.

“Incentive Plan Proposal” means the proposal to be considered at the Extraordinary General Meeting to approve the 2026 Plan.

“Insiders” means the Sponsor and certain shareholders of SPKL set forth on Schedule I of the Sponsor Agreement.

“Investment Company Act” means the Investment Company Act of 1940, as it may be amended.

“IPO” means SPKL’s initial public offering of the SPKL Units, SPKL Class A Ordinary Shares and Public Warrants pursuant to the registration statement on Form S-1 which was declared effective by the SEC on September 29, 2023 (SEC File No. 333-273176), whereby SPKL completed the offer and sale of 10,000,000 SPKL Units.

“Lead Purchaser” means Alyeska Master Fund, L.P.

“Legacy ZincFive” means ZincFive, Inc., a Delaware corporation, prior to the Closing.

“Legacy ZincFive Board” means the board of directors of Legacy ZincFive.

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“Legacy ZincFive Class A Common Stock” means the Class A common stock, par value $0.001 per share, of Legacy ZincFive.

“Legacy ZincFive Class B Common Stock” means the Class B common stock, par value $0.001 per share, of Legacy ZincFive.

“Legacy ZincFive Common Stock” means the Legacy ZincFive Class A Common Stock and Legacy ZincFive Class B Common Stock.

“Legacy ZincFive Equity Plans” means the ZincFive, Inc. 2003 Equity Incentive Plan, as amended from time to time, and the ZincFive, Inc. 2015 Equity Incentive Plan, as amended from time to time.

“Legacy ZincFive Option” means each option of Legacy ZincFive that is outstanding and unexercised immediately prior to the First Effective Time, whether vested or unvested.

“Legacy ZincFive Preferred Stock” means Legacy ZincFive’s Series A preferred stock, Series B preferred stock, Series C preferred stock, Series D preferred stock, Series E preferred stock and Legacy ZincFive Series F Stock, each with a par value of $0.001 per share.

“Legacy ZincFive Securityholders” means the securityholders of Legacy ZincFive prior to the Closing.

“Legacy ZincFive Series F Stock” means Legacy ZincFive’s Series F preferred stock, Series F-1 preferred stock, Series F-2 preferred stock, Series F-3-A preferred stock, Series F-3-B preferred stock, Series F-3-C preferred stock, Series F-3-D preferred stock and Series F-3-W preferred stock, each with a par value of $0.001 per share.

“Legacy ZincFive Warrants” means the warrants to purchase shares of Legacy ZincFive capital stock that are outstanding immediately prior to the First Effective Time, each of which will be exercised in full or expire in accordance with Section 3.05 of the Merger Agreement immediately prior to the First Effective Time.

“Letter Agreement” means that certain letter agreement, dated as of October 5, 2023, by and among SPKL, SLG SPAC Fund LLC and the members of SPKL’s board of directors and management team party thereto, as amended by the Sponsor Agreement.

“Maximum Redemption Scenario” means a scenario in which 100% of SPKL Class A Ordinary Shares currently held by Public Shareholders are redeemed for cash from the Trust Account.

“Memorandum and Articles of Association” means the amended and restated memorandum and articles of association of SPKL, as may be amended from time to time.

“Merger Agreement” means the Agreement and Plan of Merger and Reorganization, dated as of June 11, 2026, by and among SPKL, Merger Sub I, Merger Sub II and Legacy ZincFive, as may be amended, supplemented or otherwise modified from time to time in accordance with its terms. A current copy of the Merger Agreement is attached to this proxy statement/prospectus as Annex A.

“Merger Sub I” means Spark I Acquisition Corporation Sub I Inc., a Delaware corporation.

“Merger Sub II” means Spark I Acquisition Corporation Sub II LLC, a Delaware limited liability company.

“Merger Subs” collectively, means Merger Sub I and Merger Sub II. “Mergers” collectively, means the First Merger and the Second Merger.

“Modification in Recommendation” means any withdrawal, amendment, qualification or modification by the SPKL Board of its recommendation to SPKL shareholders that they vote in favor of the SPKL Stockholder Matters.

“Nasdaq” means The Nasdaq Stock Market LLC.

“No Redemption Scenario” means a scenario in which no shares of SPKL Class A Ordinary Shares currently held by Public Shareholders are redeemed.

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“Non-Convertible Note” means the non-convertible unsecured promissory note, dated June 25, 2025, issued by SPKL to the Sponsor in the principal amount of up to $2,500,000.

“NYSE” means The New York Stock Exchange.

“Organizational Documents Proposal” means the proposal to be considered at the Extraordinary General Meeting to approve by special resolution the Proposed Certificate of Incorporation and the Proposed Bylaws. A copy of each of the Proposed Certificate of Incorporation and the Proposed Bylaws is attached to this proxy statement/prospectus as Annex C and Annex D, respectively.

“Person” means any individual, firm, corporation, company, partnership, exempted limited partnership, limited liability company, incorporated or unincorporated association, joint venture, joint stock company, governmental authority or instrumentality or other entity of any kind.

“Private Placement Warrants” means the warrants purchased by the Sponsor in a private placement that closed simultaneously with the IPO, each exercisable for one SPKL Class A Ordinary Share (or, following the Domestication, one share of ZincFive Common Stock) at an exercise price of $11.50 per share.

“Proposed Bylaws” mean the proposed bylaws of ZincFive to be in effect immediately following the Domestication and Business Combination, a form of which is attached to this proxy statement/prospectus as Annex D.

“Proposed Certificate of Incorporation” means the proposed certificate of incorporation of ZincFive to be in effect immediately following the Domestication and the Business Combination, a form of which is attached to this proxy statement/prospectus as Annex C.

“Proposed Organizational Documents” means the Proposed Certificate of Incorporation and the Proposed Bylaws.

“Proxy Solicitor” means Advantage Proxy, Inc., SPKL’s proxy solicitor. “Public Shareholders” means the holders of Public Shares.

“Public Shares” means the SPKL Class A Ordinary Shares sold in the IPO (whether they were purchased in the IPO as part of the SPKL Units or following the IPO in the open market).

“Public Warrant” means the redeemable warrants included in the SPKL Units, each exercisable for one SPKL Class A Ordinary Share (or, following the Domestication, one share of ZincFive Common Stock) at an exercise price of $11.50.

“Public Warrant Holders” means the holders of the Public Warrants.

“Record Date” means         , 2026.

“Redemption” means each redemption of Public Shares for cash pursuant to the Memorandum and Articles of Association.

“Redemption Deadline” means 5:00 p.m., Eastern Time, on           , 2026 (two business days prior to the initially scheduled date of the Extraordinary General Meeting).

“Redemption Price” means an amount equal to each Public Share’s pro rata portion of the aggregate amount then on deposit in the Trust Account in accordance with the Memorandum and Articles of Association. The Redemption Price will be calculated two business days prior to the completion of the Business Combination in accordance with the Memorandum and Articles of Association.

“Sarbanes-Oxley Act” means the Sarbanes-Oxley Act of 2002. “SEC” means the U.S. Securities and Exchange Commission.

“Second Effective Time” means the date and time that the Second Merger becomes effective.

“Second Extension” means the proposal to amend our amended and restated memorandum and articles of association to extend the date by which we have to consummate an initial business combination from September 29, 2026 to March 29, 2027.

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“Second Extension Contributions” means the monthly deposits SPKL committed to make into the Trust Account, following the approval of the Second Extension at the Second Extension Meeting.

“Second Extension Meeting” means the extraordinary general meeting of SPKL’s shareholders to be held on September 25, 2026.

“Second Merger” means the merger of the Surviving Corporation, with and into Merger Sub II immediately following the First Merger, with Merger Sub II continuing as the Surviving Entity.

“Securities Act” means the U.S. Securities Act of 1933, as amended.

“Series A Preferred Investment” means the purchase of an aggregate of 10,441,174 shares of Series A Preferred Stock and, for each Series A Preferred Investor, a Series A Preferred Investor Warrant, for an aggregate purchase price of $106.5 million.

“Series A Preferred Investment Agreements” means the Series A Securities Purchase Agreement and the exhibits attached thereto.

“Series A Preferred Investor Warrants” means warrants to purchase a number of shares of ZincFive Common Stock equal to the number of shares into which such shares of ZincFive Common Stock underlying a Series A Preferred Investor’s Series A Preferred Stock are initially convertible. A copy of the form of warrant is attached to this proxy statement/prospectus as Annex L.

“Series A Preferred Stock” means the 12.0% Series A Cumulative Convertible Preferred Stock of ZincFive, par value $0.0001 per share, having the rights, preferences and privileges set forth in the Certificate of Designation.

“Series A Preferred Investors” means certain institutional and accredited investors who are party to the Series A Securities Purchase Agreement.

“Series A Securities Purchase Agreement” means the Series A Securities Purchase Agreement, dated as of June 11, 2026, by and among SPKL, Legacy ZincFive and the other purchasers identified on the signature pages thereto.

“Shareholder Proposals” means, collectively: (i) the Business Combination Proposal; (ii) the Domestication Proposal; (iii) the Stock Issuance Proposal; (iv) the Organizational Documents Proposal; (v) the Advisory Organizational Documents Proposals; (vi) the Incentive Plan Proposal; (vii) the Employee Stock Purchase Plan Proposal; and (viii) the Director Election Proposal.

“Signing Date” means June 11, 2026.

“SPKL” means Spark I Acquisition Corporation prior to the Domestication, an exempted company incorporated under the laws of the Cayman Islands. Following the Domestication, subject to shareholder approval, SPKL will be a corporation incorporated under the laws of the State of Delaware named “ZincFive, Inc.”

“SPKL Board” means the board of directors of SPKL.

“SPKL Delaware” means Spark I Acquisition Corporation as re-domiciled in the State of Delaware pursuant to the Domestication, prior to the consummation of the Mergers.

“SPKL Class A Ordinary Shares” means the Class A ordinary shares of SPKL, par value $0.0001 per share.

“SPKL Class B Ordinary Shares” means the Class B ordinary shares of SPKL, par value $0.0001 per share.

“SPKL Delaware Warrants” means the warrants of SPKL Delaware, issued upon conversion of the SPKL Warrants immediately upon the effectiveness of the Domestication.

“SPKL Insiders” means certain shareholders of SPKL, other than the Sponsor, each of whom is a member of the SPKL Board and/or management team and a party to the Letter Agreement.

“SPKL Ordinary Shares” collectively, means the SPKL Class A Ordinary Shares and the SPKL Class B Ordinary Shares.

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“SPKL Stockholder Matters” means (i) the Merger Agreement and the Business Combination; (ii) the Domestication; (iii) the Charter and Bylaws of ZincFive; (iv) the issuance of shares of ZincFive Common Stock as required by the listing rules of Nasdaq; (v) the adoption of the 2026 Plan and ESPP; (vi) the election of members of the ZincFive Board (in the form of an advisory vote, with the directors being elected by written resolution of the holders of SPKL Class B Ordinary Shares in accordance with our Memorandum and Articles of Association); (vii) the amendment of our organizational documents to remove references to the $5,000,001 net tangible assets requirement set forth in our Memorandum and Articles of Association; (viii) any other proposals as the SEC may indicate are necessary in its comments to this proxy statement/ prospectus; (ix) any proposals the parties agree are necessary or desirable to consummate the Business Combination; and (x) adjournment of the Extraordinary General Meeting, if necessary.

“SPKL Units” means the units sold in the IPO, each consisting of one SPKL Class A Ordinary Share and one-half of one Public Warrant.

“SPKL Warrants” means the Public Warrants and the Private Placement Warrants, each exercisable for one SPKL Class A Ordinary Share at an exercise price of $11.50 per share, subject to adjustment.

“Sponsor” means SLG SPAC Fund LLC, a Delaware limited liability company and an affiliate of SparkLabs Group Management, LLC.

“Sponsor Agreement” means that certain agreement, dated June 11, 2026, by and among SPKL, Legacy ZincFive and certain shareholders of SPKL set forth on Schedule I thereto and as amended by the Amendment to Sponsor Agreement, dated September 28, 2026.

“Stock Exchange” means the NYSE, Nasdaq, or such other securities exchange as mutually agreed by SPKL and Legacy ZincFive.

“Stock Issuance Proposal” means the proposal to be considered at the Extraordinary General Meeting to approve the issuance (or reservation for issuance) of: (i) shares of ZincFive Common Stock in connection with the Business Combination; (ii) shares of Series A Preferred Stock and Series A Preferred Investor Warrants; (iii) shares of ZincFive Common Stock issuable upon conversion of such Series A Preferred Stock and upon exercise of such Series A Preferred Investor Warrants; (iv) shares of ZincFive Common Stock to the Lead Purchaser and certain of the First Tranche Bridge Investors pursuant to the Sponsor Agreement; and (v) any other preferred stock, common stock and securities convertible into or exercisable for common stock pursuant to subscription, purchase or similar agreements SPKL has entered, or may enter, into prior to Closing, in each case for purposes of complying with the applicable provisions of the Nasdaq Listing Rules.

“Surviving Corporation” means Legacy ZincFive, as the surviving corporation after the consummation of the First Merger.

“Surviving Entity” means Merger Sub II, as the surviving entity after the consummation of the Second Merger.

“Transaction Agreements” means the Merger Agreement, the Sponsor Agreement, the A&R Registration Rights Agreement, the Company Support Agreements, the Proposed Organizational Documents, the Series A Securities Purchase Agreement and all of the agreements, documents, instruments and certificates entered into in connection herewith or therewith and any and all exhibits and schedules thereto.

“Transactions” means the transactions contemplated by the Merger Agreement, the Transaction Agreements and the Series A Preferred Investments.

“Transfer Agent” means Continental Stock Transfer & Trust Company.

“Trust Account” means the trust account of SPKL, which holds the net proceeds from the IPO and the sale of the Private Placement Warrants, together with interest earned on the net proceeds, less amounts released to pay taxes.

“Trust Agreement” means the Investment Management Trust Agreement, dated as of October 5, 2023, by and between SPKL and Continental Stock Transfer & Trust Company, as trustee.

“Warrant Agreement” means the Warrant Agreement, dated as of October 5, 2023, by and between SPKL and the Transfer Agent, which governs the outstanding Public Warrants.

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“Working Capital Warrants” means the warrants issuable upon the conversion of up to $1,500,000 of the aggregate outstanding principal balance of the Convertible Note, at a price of $1.00 per warrant, on the same terms as the Private Placement Warrants.

“ZincFive” means SPKL as of and following the Domestication, whose name will be changed to ZincFive, Inc.

“ZincFive Board” means the board of directors of ZincFive.

“ZincFive Common Stock” means the common stock of ZincFive, par value $0.0001 per share.

“ZincFive OpCo” means ZincFive Technologies, Inc. (formerly known as ZincFive, Inc.), a Delaware corporation and direct wholly-owned subsidiary of ZincFive following the consummation of the Business Combination.

“ZincFive Warrant” means a redeemable warrant exercisable for one share of ZincFive Common Stock.

Share Calculations and Ownership Percentages

Unless otherwise specified (including in the sections of this proxy statement/prospectus entitled “Unaudited Pro Forma Condensed Combined Financial Information” and “Beneficial Ownership of Securities”), the share calculations and ownership percentages set forth in this proxy statement/prospectus with respect to ZincFive’s stockholders following the Closing are for illustrative purposes only and assume the following:

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MARKET AND INDUSTRY DATA

This proxy statement/prospectus contains estimates and information concerning Legacy ZincFive’s industry, including market size of the markets in which Legacy ZincFive participates, that are based on various third-party sources, industry publications and reports, as well as Legacy ZincFive’s own internal information. This information involves assumptions and limitations, and you are cautioned not to give undue weight to such estimates and information. The markets in which Legacy ZincFive operates are subject to a high degree of uncertainty and risk due to a variety of factors, including those described in the section entitled “Risk Factors.” These and other factors could cause results to differ materially from those expressed in these sources, publications and reports.

The sources of certain statistical data, estimates and forecasts contained in this proxy statement/ prospectus include the following independent industry publications or reports.

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CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This proxy statement/prospectus contains forward-looking statements within the meaning of the federal securities laws, which statements involve substantial risks and uncertainties and include SPKL’s or Legacy ZincFive’s or their management teams’ expectations, hopes, beliefs, intentions or strategies regarding the future. You can identify forward-looking statements because they contain words such as “anticipate,” “believe,” “contemplate,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “plan,” “potential,” “predict,” “project,” “seek,” “should,” “target,” “will,” “would” or the negative of these words or other similar terms or expressions that predict or indicate future events or trends or that are not statements of historical matters, but the absence of these words does not mean that a statement is not forward-looking. Unless the context indicates or requires otherwise, references in this section to “we,” “us” and “our” refer to SPKL and Legacy ZincFive. Forward-looking statements contained in this proxy statement/prospectus include, for example, statements about:

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We caution you that the foregoing list may not contain all of the forward-looking statements made in this proxy statement/prospectus. We advise you that the safe harbor afforded by the Private Securities Litigation Reform Act of 1995 to certain forward-looking statements does not extend to forward-looking statements made by us in connection with this proxy statement/prospectus.

You should not rely upon forward-looking statements as predictions of future events. SPKL and Legacy ZincFive have each based the forward-looking statements contained in this proxy statement/ prospectus primarily on their respective current expectations and projections about future events and trends that they believe may affect their business, operating results, financial condition and prospects. The outcome of the events described in these forward-looking statements is subject to risks, uncertainties and other factors, including those described in the section entitled “Risk Factors” and elsewhere in this proxy statement/ prospectus. Moreover, we operate in a very competitive and rapidly changing environment. New risks and uncertainties emerge from time to time, and it is not possible for us to predict all risks and uncertainties that could have an impact on the forward-looking statements contained in this proxy statement/prospectus. We cannot assure you that the results, events and circumstances reflected in the forward-looking statements will be achieved or occur, and actual results, events or circumstances could differ materially from those described in the forward-looking statements.

Neither we nor any other person assumes responsibility for the accuracy and completeness of any of these forward-looking statements. Moreover, the forward-looking statements made in this proxy statement/ prospectus relate only to events as of the date on which the statements are made. We undertake no obligation to update any forward-looking statements made in this proxy statement/prospectus to reflect events or circumstances after the date of this proxy statement/prospectus or to reflect new information or the occurrence of unanticipated events, except as required by law. You should not place undue reliance on our forward-looking statements. Our forward-looking statements do not reflect the potential impact of any future acquisitions, mergers, dispositions, joint ventures or investments we may make following the Closing.

In addition, statements that “we believe” and similar statements reflect our beliefs and opinions on the relevant subject. These statements are based upon information available to us as of the date of this proxy statement/prospectus, and while we believe such information forms a reasonable basis for such statements, such information may be limited or incomplete, and our statements should not be read to indicate that we have conducted an exhaustive inquiry into, or review of, all potentially available relevant information. These statements are inherently uncertain and investors are cautioned not to unduly rely upon these statements.

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QUESTIONS AND ANSWERS FOR SHAREHOLDERS OF SPKL

The questions and answers below highlight only selected information from this proxy statement/ prospectus and only briefly address some commonly asked questions about the proposals to be presented at the Extraordinary General Meeting, including with respect to the Business Combination. The following questions and answers do not include all the information that may be important to SPKL’s shareholders. SPKL urges shareholders to read this proxy statement/prospectus, including the annexes and the other documents referred to in this proxy statement/prospectus, carefully and in their entirety to fully understand the Business Combination and the voting procedures for the Extraordinary General Meeting, which will be held at      , Eastern Time, on                             , 2026, electronically at     . To participate in the Extraordinary General Meeting online, visit           and enter the 12-digit control number included on your proxy card. If you hold your shares through a bank, broker or other nominee, you will need to take additional steps to participate in the Extraordinary General Meeting, as described in this proxy statement/prospectus.

Q.Why am I receiving this proxy statement/prospectus?

You are receiving this proxy statement/prospectus in connection with the Extraordinary General Meeting. SPKL is holding the Extraordinary General Meeting to, among other things, obtain the approvals required for the Business Combination and the other transactions contemplated by the Merger Agreement. See the section entitled “The Business Combination Proposal” of this proxy statement/prospectus for additional information.

A current copy of the Merger Agreement is attached to this proxy statement/prospectus as Annex A. You are encouraged to carefully read this proxy statement/prospectus and the Merger Agreement in their entirety.

SPKL is sending this proxy statement/prospectus to its shareholders to help them decide how to vote their SPKL Ordinary Shares with respect to the matters to be considered at the Extraordinary General Meeting. The Business Combination cannot be completed unless SPKL’s shareholders approve the Condition Precedent Proposals set forth in this proxy statement/prospectus. Information about the Extraordinary General Meeting, the Business Combination and the other business to be considered by shareholders at the Extraordinary General Meeting is contained in this proxy statement/prospectus.

This document constitutes a proxy statement and a prospectus of SPKL. It is a proxy statement because the SPKL Board is soliciting proxies from its shareholders using this proxy statement/prospectus. It is a prospectus because SPKL, in connection with the Business Combination, is offering shares of ZincFive Common Stock in exchange for (i) SPKL Class A Ordinary Shares (including those converted from SPKL Class B Ordinary Shares), (ii) shares of Legacy ZincFive Preferred Stock, and (iii) shares of Legacy ZincFive Common Stock (including Legacy ZincFive Class A Common Stock and Legacy ZincFive Class B Common Stock), in each case outstanding as of the relevant time, each as described in this proxy statement/prospectus. See the section entitled “The Business Combination Proposal — The Merger Agreement — Merger Consideration” of this proxy statement/prospectus for additional information.

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THE VOTE OF PUBLIC SHAREHOLDERS IS IMPORTANT. PUBLIC SHAREHOLDERS ARE ENCOURAGED TO VOTE AS SOON AS POSSIBLE AFTER CAREFULLY REVIEWING THIS PROXY STATEMENT/PROSPECTUS, INCLUDING THE ANNEXES AND THE ACCOMPANYING FINANCIAL STATEMENTS OF SPKL AND LEGACY ZINCFIVE, IN ITS ENTIRETY.

Q.What proposals are shareholders of SPKL being asked to vote upon?

If SPKL’s shareholders do not approve each of the Condition Precedent Proposals, then unless certain conditions in the Merger Agreement are waived by the applicable parties to the Merger Agreement, the Merger Agreement could be terminated, and the Business Combination may not be consummated. See the sections of this proxy statement/prospectus entitled “The Business Combination Proposal,” “The Domestication Proposal,” “The Stock Issuance Proposal,” “The Organizational Documents Proposal,” “The Incentive Plan Proposal,” “The Employee Stock Purchase Plan Proposal,” and “The Director Election Proposal.”

SPKL will hold the Extraordinary General Meeting to consider and vote upon these proposals. This proxy statement/prospectus contains important information about the Business Combination and the other matters to be acted upon at the Extraordinary General Meeting. Shareholders of SPKL should read it carefully.

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After careful consideration, the SPKL Board has unanimously determined that each of: (i) the Business Combination Proposal; (ii) the Domestication Proposal; (iii) the Stock Issuance Proposal; (iv) the Organizational Documents Proposal; (v) the Advisory Organizational Documents Proposals; (vi) the Incentive Plan Proposal; (vii) the Employee Stock Purchase Plan Proposal; (viii) the Director Election Proposal; and (ix) the Adjournment Proposal, if presented to the Extraordinary General Meeting, is in the best interests of SPKL. Accordingly, the SPKL Board unanimously recommends that you vote or give instruction to vote “FOR” each of those proposals.

The existence of financial and personal interests of one or more of SPKL’s directors may result in a conflict of interest on the part of such director(s) between what such director may believe is in the best interests of SPKL and its shareholders and what such director may believe is best for themselves in determining to recommend that shareholders vote for the proposals. Certain of SPKL’s directors and officers have interests in the Business Combination that may be different from, or in addition to, your interests as a shareholder, and there may be actual or potential material conflicts of interests between or among (i) the Sponsor, SPKL, SPKL’s officers and directors, and Legacy ZincFive’s officers and directors and (ii) unaffiliated security holders of SPKL. See the sections of this proxy statement/prospectus entitled “The Business Combination Proposal — Certain Interests of SPKL’s Directors and Officers and Others in the Business Combination” and “The Business Combination Proposal — Certain Interests of Legacy ZincFive’s Directors and Officers in the Business Combination” for a further discussion of these considerations.

Q.Are the proposals conditioned on one another?

Q.Why is SPKL proposing the Business Combination?

Legacy ZincFive is a leader in immediate power solutions for the data center and artificial intelligence infrastructure markets, powered by its proprietary nickel-zinc battery technology. Based on SPKL’s due diligence investigations of Legacy ZincFive and the industry in which it operates, including the financial and other information provided by Legacy ZincFive in the course of SPKL’s due diligence, the SPKL Board believes that the Business Combination with Legacy ZincFive is in the best interests of SPKL and its shareholders and presents an opportunity to increase shareholder value. See the section of this proxy statement/prospectus entitled “The Business Combination Proposal — The SPKL Board’s Reasons for the Approval of the Business Combination” for additional information.

Q.What will Legacy ZincFive Securityholders receive in connection with the Business Combination?

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See the section of this proxy statement/prospectus entitled “The Business Combination Proposal — The Merger Agreement — Merger Consideration” for additional information.

The obligations of Legacy ZincFive and SPKL to complete the Mergers are not conditioned on the receipt of opinions of U.S. tax counsel to the effect that the Mergers will qualify as a reorganization for U.S. federal income tax purposes. If the Mergers do not qualify as a reorganization, the Mergers will be treated as a taxable stock sale and each U.S. holder of Legacy ZincFive Common Stock and Legacy ZincFive Preferred Stock will generally recognize capital gain or loss, for U.S. federal income tax purposes, on the receipt of ZincFive Common Stock issued to such holders of Legacy ZincFive Common Stock and Legacy ZincFive Preferred Stock.

Please review the information in the section entitled “Material U.S. Federal Income Tax Considerations of the Mergers” of this proxy statement/prospectus for a more complete description of the material U.S. federal income tax consequences of the Mergers to Legacy ZincFive U.S. Holders. The discussion of the material U.S. federal income tax consequences contained in this proxy statement/prospectus is intended to provide only a general discussion. The tax consequences of the Mergers to any particular Legacy ZincFive Securityholder will depend on that securityholder’s particular facts and circumstances. Accordingly, you are urged to consult your own tax advisor to determine your tax consequences from the Mergers, including the applicability and effect of U.S. federal, state and local and non-U.S. income and other tax laws in light of your particular circumstances.

SPKL and Legacy ZincFive cannot predict how many Public Shares will be redeemed. As a result, SPKL and Legacy ZincFive are presenting two different redemption scenarios in the tables below with respect to SPKL Class A Ordinary Shares, each of which presents a different allocation of total ZincFive equity following the Closing. The number of Public Shares redeemed in connection with the Business Combination and the ownership percentages of Public Shareholders may differ from the presentation below if the actual redemptions are different from these assumptions. See the section of this proxy statement/prospectus entitled “Risk Factors — Risks Related to SPKL — The ability of our Public Shareholders to exercise redemption rights with respect to a portion of our Public Shares could increase the probability that the Business Combination will be unsuccessful and that you would have to wait for liquidation for your Public Shares to be redeemed.”

To illustrate potential dilution in each such scenario, the tables below present the post-Closing share ownership of ZincFive under each of: (i) the No Redemption Scenario and (ii) the Maximum Redemption Scenario. The first table excludes the dilutive effect of: (i) the Private Placement Warrants; (ii) the Public Warrants; (iii) the Working Capital Warrants into which the Convertible

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Note can be converted; and (iv) the Series A Preferred Investor Warrants. The second table includes the dilutive effect of such items.

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*      Amounts may not sum due to rounding.

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For more information, please see the sections of this proxy statement/prospectus entitled “Unaudited Pro Forma Condensed Combined Financial Information” and “Beneficial Ownership of Securities.”

Pursuant to the Merger Agreement, SPKL and ZincFive have agreed to use their commercially reasonable efforts to obtain commitments from one or more additional investors for additional private financing prior to or substantially concurrently with the Closing, on terms mutually agreed by SPKL and ZincFive. From time to time following execution of the Merger Agreement and prior to the Closing, SPKL may enter into additional subscription agreements on forms mutually acceptable to SPKL and ZincFive. Any such additional financing would be in addition to the Series A Preferred Investment described above.

For more information, see the section of this proxy statement/prospectus entitled “The Business Combination Proposal — Certain Agreements Related to the Business Combination — Series A Securities Purchase Agreement.”

A copy of the form of Series A Securities Purchase Agreement is attached to this proxy statement/ prospectus as Annex J, which you are encouraged to read in its entirety.

To effect the Domestication, SPKL will file an application to deregister with the Registrar of Companies in the Cayman Islands, together with the necessary accompanying documents and fees, and file the Proposed Certificate of Incorporation and a certificate of corporate domestication with the Secretary of State of the State of Delaware, pursuant to which SPKL will be domesticated and continue as a Delaware corporation.

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The approval of the Domestication Proposal is a condition to the Closing under the Merger Agreement. The approval of the Domestication Proposal requires a special resolution under the Companies Act and the Memorandum and Articles of Association, being the affirmative vote of the holders of at least two-thirds of the votes cast by the holders of the issued SPKL Ordinary Shares, voting together as a single class, who, being present in person, virtually or by proxy and entitled to vote at the Extraordinary General Meeting, vote in favor of the Domestication Proposal at the Extraordinary General Meeting. Pursuant to Article 182 of the Memorandum and Articles of Association, with respect to any vote on the Domestication, holders of SPKL Class B Ordinary Shares will have ten votes for every SPKL Class B Ordinary Share and holders of SPKL Class A Ordinary Shares will have one vote for every SPKL Class A Ordinary Share. Abstentions and broker non-votes, while considered present for the purposes of establishing a quorum, will not count as votes cast at the Extraordinary General Meeting and otherwise will have no effect on a particular proposal.

SPKL does not expect to have significant cumulative earnings and profits, if any, on the date of the Domestication. However, the determination of earnings and profits is complex and may be impacted by numerous factors (including matters discussed in this proxy statement/prospectus). It is possible that the amount of SPKL’s cumulative net earnings and profits could be positive through the date of the Domestication.

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As discussed more fully under “Material U.S. Federal Income Tax Considerations Related to SPKL Securityholders,” SPKL believes that it is likely classified as a PFIC for U.S. federal income tax purposes. If SPKL were classified as a PFIC for U.S. federal income tax purposes, then notwithstanding the U.S. federal income tax consequences of the Domestication discussed above, proposed Treasury Regulations under Section 1291(f) of the Code and certain other PFIC rules (which have retroactive proposed effective dates), if finalized in their current form, generally would require a U.S. Holder to recognize gain on the exchange of SPKL Ordinary Shares or SPKL Warrants for ZincFive Common Stock or ZincFive Warrants pursuant to the Domestication. Any such gain would be taxable income with no corresponding receipt of cash in the Domestication. The tax on any such gain would be imposed at the rate applicable to ordinary income and an interest charge would apply based on a complex set of rules. The proposed Treasury Regulations provide coordinating rules with other sections of the Code, including Section 367(b), which affect the manner in which the rules under such other sections apply to transfers of PFIC stock. However, it is difficult to predict whether, in what form, and with what effective date, final Treasury Regulations under Section 1291(f) of the Code and such other PFIC rules may be adopted and how any such Treasury Regulations would apply. Importantly, however, U.S. Holders that make or have made certain elections discussed further under “Material U.S. Federal Income Tax Considerations Related to SPKL Securityholders” with respect to their SPKL Ordinary Shares are generally not subject to the same gain recognition rules under the currently proposed Treasury Regulations under Section 1291(f) of the Code. Under current law, no such elections may be made with respect to SPKL Warrants. For a more complete discussion of the potential application of the PFIC rules to U.S. Holders as a result of the Domestication, see the section of this proxy statement/prospectus entitled “Material U.S. Federal Income Tax Considerations Related to SPKL Securityholders.”

Additionally, the Domestication may cause Non-U.S. Holders (as defined in “Material U.S. Federal Income Tax Considerations Related to SPKL Securityholders”) to become subject to U.S. federal withholding taxes on any amounts treated as dividends paid in respect of such Non-U.S. Holder’s ZincFive Common Stock after the Domestication.

The tax consequences of the Domestication are complex and will depend on a holder’s particular circumstances. All holders of SPKL Ordinary Shares or SPKL Warrants are urged to consult their tax advisor regarding the tax consequences to them of the Domestication, including the applicability and effect of U.S. federal, state and local and non-U.S. tax laws and the application of the PFIC rules. For a more complete discussion of the U.S. federal income tax considerations of the Domestication, see the section of this proxy statement/prospectus entitled “Material U.S. Federal Income Tax Considerations Related to SPKL Securityholders.”

Q.Do I have redemption rights?

Notwithstanding the foregoing, a Public Shareholder, together with any affiliate of such Public Shareholder or any other person with whom such Public Shareholder is acting in concert or as a “group” (as defined in Section 13(d)(3) of the Exchange Act), will be restricted from redeeming its Public Shares with respect to more than an aggregate of 15% of the Public Shares sold in our IPO. Accordingly, if a Public Shareholder, alone or acting in concert or as a group, seeks to redeem more than 15% of the Public Shares sold in our IPO, then any such shares in excess of that 15% limit would not be redeemed for cash.

The Insiders have agreed to waive their redemption rights with respect to all SPKL Ordinary Shares held by them in connection with the Closing. As a result, the shares held by the Sponsor and SPKL’s officers and directors will not be taken into account in calculating the per-share Redemption Price payable to Public Shareholders who elect to redeem their Public Shares.

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Holders must complete the procedures for electing to redeem their Public Shares in the manner described above prior to 5:00 p.m., Eastern Time, on          , 2026 (two business days before the initially scheduled date of the Extraordinary General Meeting) in order for their Public Shares to be redeemed.

The address of the Transfer Agent is listed under the question “Who can help answer my questions?” of this proxy statement/prospectus.

Public Shareholders will be entitled to request that their Public Shares be redeemed for the Redemption Price. For illustrative purposes, as of           , 2026, this would have amounted to approximately $          per issued and outstanding Public Share. However, the proceeds deposited in the Trust Account could become subject to the claims of SPKL’s creditors, if any, which could have priority over the claims of the Public Shareholders. The per share distribution from the Trust Account in such a situation may be less than originally expected due to such claims. Whether you vote, and if you do vote, how you vote, on any proposal, including the Business Combination Proposal, will have no impact on the amount you will receive upon exercise of your redemption rights. The redemption of Public Shares will be effected while SPKL remains a Cayman Islands exempted company, prior to the Domestication, and it is expected that the Redemption Price will be paid to Public Shareholders electing to redeem their Public Shares promptly following the Closing.

Any request for redemption, once made by a holder of Public Shares, may not be withdrawn following the Redemption Deadline, unless the SPKL Board determines (in its sole discretion) to permit such withdrawal of a redemption request (which it may do in whole or in part). Furthermore, if a holder of a Public Share delivers its share certificates (if any) along with the redemption forms in connection with an election of its redemption and subsequently decides prior to the Redemption Deadline not to elect to exercise such rights, it may simply request that SPKL permit the withdrawal of the request for redemption and instruct the Transfer Agent to return the share certificates (physically or electronically). The holder can make such request by contacting the Transfer Agent at the address or email address listed in this proxy statement/prospectus.

Any corrected or changed written exercise of redemption rights must be received by the Transfer Agent at least two business days prior to the initially scheduled date of the Extraordinary General Meeting. No request for redemption will be honored unless the holder’s certificates for Public Shares (if any) along with the redemption forms have been delivered (either physically or electronically) to the Transfer Agent, at least two business days prior to the initially scheduled date of the Extraordinary General Meeting.

If a holder of Public Shares properly makes a request for redemption and the certificates for Public Shares (if any) along with the redemption forms are delivered as described above, then, if the Business Combination is consummated, SPKL will effect the redemption of such Public Shares while SPKL remains a Cayman Islands exempted company, and pay the Redemption Price, calculated as of two business days prior to the Closing, promptly following the Closing. If the Business Combination is not consummated, the Public Shares will be returned to the respective holder, broker or bank. Although SPKL will effect the redemption prior to the Domestication, because the Redemption Price will be paid following the Closing, U.S. Holders of Public Shares (as defined in section of this proxy statement/ prospectus entitled “Material U.S. Federal Income Tax Considerations Related to SPKL Securityholders”) exercising redemption rights may be subject to the potential tax consequences of the Domestication. For a more complete discussion of the U.S. federal income tax considerations of an exercise of redemption rights, see the section of this proxy statement/prospectus entitled “Material U.S. Federal Income Tax Considerations Related to SPKL Securityholders.”

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If you are a holder of Public Shares and you exercise your redemption rights, such exercise will not result in the loss of any Public Warrants that you may hold.

Assuming that no more than         Public Shares, representing 50% of the number of Public Shares outstanding as of the date of this proxy statement/prospectus are redeemed for an aggregate payment of $          million from the Trust Account, which is a potential amount of redemptions, and assuming that each redeeming Public Shareholder holds one-half of one Public Warrant for each Public Share being redeemed (representing the number of Public Warrants included in each SPKL Unit) and using the closing warrant price on Nasdaq of $         as of           , 2026, the aggregate fair value of Public Warrants that can be retained by redeeming Public Shareholders is $             million. Assuming the Maximum Redemption Scenario, resulting in Public Shares redeemed for an aggregate payment of $           million from the Trust Account, and assuming that each redeeming Public Shareholder holds one-half of one Public Warrant for each Public Share being redeemed (representing the number of Public Warrants included in each SPKL Unit) and using the closing warrant price on Nasdaq of $           as of           , 2026, the aggregate fair value of Public Warrants that can be retained by redeeming Public Shareholders is $           million. The actual market price of the Public Warrants may be higher or lower on the date that warrant holders seek to sell such Public Warrants. Additionally, SPKL cannot assure the holders of warrants that they will be able to sell their Public Warrants in the open market as there may not be sufficient liquidity in such securities when warrant holders wish to sell their Public Warrants. Further, while the level of redemptions of Public Shares will not directly change the value of the warrants because the warrants will remain outstanding regardless of the level of redemptions, as redemptions of Public Shares increase, all holders of ZincFive Warrants following the Closing who exercise such ZincFive Warrants will ultimately own a greater interest in ZincFive because there would be fewer shares outstanding overall.

Following the Closing, ZincFive may redeem your unexpired Public Warrants prior to their exercise at a time that is disadvantageous to you, making your warrants worthless. ZincFive may redeem outstanding Public Warrants at any time after they become exercisable and prior to their expiration, at a price of $0.01 per warrant. To exercise such redemption right: (i) the last reported sale price of ZincFive Common Stock must equal or exceed $18.00 per share (as may be adjusted in certain circumstances including in the event of a share dividend, or recapitalization, reorganization, merger or consolidation) on each of 20 trading days within the 30 trading-day period ending on the third business day prior to the date on which we send notice of redemption to the warrant holders; and (ii) certain other conditions must be met. If and when the Public Warrants become redeemable by ZincFive, we may exercise our redemption rights even if we are unable to register or qualify the underlying securities for sale under all applicable state securities laws. As a result, ZincFive may redeem the Public Warrants as set forth above even if the holders are otherwise unable to exercise the Public Warrants. Redemption of the outstanding Public Warrants could force you to: (A) exercise your Public Warrants and pay the exercise price of $11.50 per share at a time when it may be disadvantageous for you to do so; (B) sell your Public Warrants at the then-current market price when you might otherwise wish to hold your Public Warrants; or (C) accept the nominal redemption price of $0.01 per warrant, which, at the time the outstanding Public Warrants are called for redemption, is likely to be substantially less than the market value of your Public Warrants.

If ZincFive calls the Public Warrants for redemption, the ZincFive Board will have the option to require all holders that wish to exercise the Public Warrants to do so on a “cashless basis,” as described in the Warrant Agreement. The exercise price and number of shares of ZincFive Common Stock issuable upon exercise of the Public Warrants may be adjusted in certain circumstances including in the event of a share dividend, or recapitalization, reorganization, merger or consolidation. However, the Public Warrants will not be adjusted for issuance of ZincFive Common Stock at a price below its exercise price. In no event will ZincFive be required to net cash settle the Public Warrants.

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If, prior to the Closing, (x) SPKL issues additional SPKL Class A Ordinary Shares or equity-linked securities for capital raising purposes in connection with the Closing at an issue price or effective issue price of less than $9.20 per SPKL Class A Ordinary Share (with such issue price or effective issue price to be determined in good faith by the SPKL Board and, in the case of any such issuance to SPKL’s initial shareholders or their respective affiliates, without taking into account any Founder Shares held by SPKL’s initial shareholders or such affiliates, as applicable, prior to such issuance) (the “Newly Issued Price”), (y) the aggregate gross proceeds from such issuances represent more than 60% of the total equity proceeds, and interest thereon, available for the funding of the Business Combination on the Closing Date (net of redemptions), and (z) the VWAP of the SPKL Class A Ordinary Shares during the 20 trading day period starting on the trading day prior to the Closing Date (such price, the “Market Value”) is below $9.20 per share, then the exercise price of the warrants will be adjusted (to the nearest cent) to be equal to 115% of the higher of the Market Value and the Newly Issued Price, and the $18.00 per share redemption trigger price shall be adjusted (to the nearest cent) to be equal to 180% of the higher of the Market Value and the Newly Issued Price.

If SPKL is unable to complete the Business Combination within the Combination Period, and SPKL liquidates the funds held in the Trust Account, holders of the Public Warrants will not receive any of such funds with respect to their Public Warrants, nor will they receive any distribution from SPKL’s assets held outside of the Trust Account with respect to such Public Warrants. Accordingly, the Public Warrants may expire worthless.

All shareholders considering exercising redemption rights are urged to consult their tax advisor on the tax consequences to them of an exercise of redemption rights, including the applicability and effect of U.S. federal, state and local and non-U.S. tax laws.

Upon the Closing, the funds deposited in the Trust Account will be released to pay holders of Public Shares who properly exercise their redemption rights; to pay transaction fees and expenses associated with the Business Combination; and for working capital and general corporate purposes of ZincFive following the Business Combination. See the section of this proxy statement/prospectus entitled “Summary of the Proxy Statement/Prospectus — Sources and Uses of Funds for the Business Combination.”

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The following table illustrates the effective underwriting discount on a percentage basis of the amount of cash in the Trust Account available to ZincFive at each redemption level identified below, and includes: (i) the cash underwriting fee that was paid in connection with the IPO; and (ii) the payment of the deferred underwriting fees payable upon the consummation of the Business Combination, each of which is not adjusted for redemptions: