Undead Fortitude. If damage reduces the creature to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the zombie drops to 1 hit point instead.

Infection. Every time a living creature is hit by the Undead Talons attack, it must make a DC 10 Strength, Dexterity, or Constitution saving throw, its choice. On a failed save, the creature is hit on an exposed limb, and is now Infected. An Infected creature loses 1 maximum hp each day until it reaches 0 hp (not max hp). Once reaching 0 hp, the Infected creature becomes a Zombie at with 22 hp. Only the removal of their tainted limb before their next long rest or a Greater Restoration spell can end the Infection.

Undead Talons. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 1 slashing damage + 1 necrotic damage.