X0609 4 2026-10-09 0 0001937653 Zymeworks Inc. ZYME 0002127119 Schayowitz Adam false C/O ZYMEWORKS INC. 108 PATRIOT DRIVE, SUITE A MIDDLETOWN DE 19709 0 1 0 0 EVP, Head of R&D 0 Common Stock 2026-10-09 4 M 0 37037 0 A 37037 D Common Stock 2026-10-09 4 S 0 13832 25.85 D 23205 D Restricted Stock Unit 2026-10-09 4 M 0 37037 0 D Common Stock 37037 74074 D Represents shares of common stock issued upon vesting of one third of the restricted stock units ("RSUs") granted on October 9, 2025. Represents shares of common stock sold to cover tax withholding obligations and other applicable fees in connection with the vesting of RSUs pursuant to mandatory "sell to cover" provisions contained in the Reporting Person's applicable RSU grant agreement, and does not represent a discretionary sale by the Reporting Person. The Reporting Person did not sell or otherwise dispose of any of the shares reported on this Form 4 for any reason other than to cover required taxes and fees. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $25.85 to $25.88, inclusive. Upon request by the Commission staff, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price. Each RSU represents the contingent right to receive, upon vesting of the RSU, one share of common stock. Restricted stock units ("RSUs") granted October 9, 2025; vest in three equal annual installments beginning October 9, 2026. /s/ Catherine Graham, Attorney-in-Fact 2026-10-09