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.

Pack Tactics. The zombie wolf has advantage on attack rolls against a creature if at least one of the zombie wolf's allies is within 5 feet of the creature and the ally isn't incapacitated.

Bite. Melee Weapon Attack: +5, Reach 5 ft., one target Hit: 10 (3d4+3) piercing damage. 

Target must succeed a DC 13 STR save or be knocked prone.