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.

Horde Rush. If excited and attracted, the Zombie Horde will storm the thing that excited it. The Horde will dash at 50 ft. per round. Creatures and structures that fall victim to the horde will take 1d4 damage for each Zombie in the horde, as determined by a d100+10. 

If surrounded by the horde, each target will take attacks equal to 1/3 of the hordes number. If not surrounded, they will take 1/4 of the hordes number. 

Slam. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 4 (1d6 + 1) bludgeoning damage.

Bite. +3 to hit, reach 5 ft., one target. Hit: 8 (2d6+3) piercing. Target must succeed on a DC 10 Constitution throw or take 1d4 poison damage.