Why is زَيْدٍ allowed in مَا سَلَّمْتُ عَلَى الْقَادِمِيْنَ إِلَّا زَيْدٍ?

Mustathna: Excluding a Member

• It follows the genitive case of the stated group noun.
• Every proper name after إِلَّا is genitive.
• It is the subject of سَلَّمْتُ.
• Negation always makes the final noun genitive.