Undead Fortitude. If damage reduces the zombie 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.
Rotting Fist. Melee Weapon Attack: +4 to hit, reach 5ft, one creature. Hit 5(1d6 +2) Bludgeoning damage + 1d4 Poison damage.