Spark I Acquisition Corp

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:

statement/prospectus as Annex H, including the authorization of the initial share reserve thereunder (the “Incentive Plan Proposal”); (vii) approve the ZincFive, Inc. 2026 Employee Stock Purchase Plan, a form of which is attached to this proxy statement/prospectus as Annex I, including the authorization of the initial share reserve thereunder (the “Employee Stock Purchase Plan Proposal”); (viii) approve the election of directors to serve on the board of directors of ZincFive, each until such director’s successor is duly elected and qualified or until such director’s earlier death, resignation or removal (the “Director Election Proposal”); and (ix) approve the adjournment of the Extraordinary General Meeting to a later date or dates, if necessary, (a) to permit further solicitation of proxies in the event that there are insufficient votes for the approval of one or more proposals at the Extraordinary General Meeting, (b) for absence of a quorum, (c) to allow reasonable additional time for the filing or mailing of any supplemental or amended disclosure, or (d) to engage with investors (“Adjournment Proposal”); and