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.

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) piercing damage. Any creature that is bitten is also Poisoned. The Poisoned creature takes 1d6 Necrotic damage at the start of each day, subtracting this damage from the maximum hitpoints. this cannot be cured. when a creature poisoned in this way dies it rises from its grave 1d6 days later as an undead that best fits its statistics. This undead is fully under the control of the controller of the Zombie that turned it