Keen Hearing. The zombie wolf has advantage on Wisdom (Perception) checks that rely on hearing.

Pack Tactics. (If master is able to see and issue orders.) The 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.

Undead Fortitude. If damage reduces the zombie wolf 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 wolf drops to 1 hit point instead.

Necrotic Bite. Melee Weapon Attack: +6 to hit, reach 5ft., one target. Hit: 9 (2d4 +4) piercing damage and 2 (1d4) necrotic Damage.