Shapechanger. The zombie werewolf can use its action to polymorph into a decaying wolf-humanoid hybrid or into a rotting wolf, or back into its true form, which is an undead humanoid. Its statistics, other than its AC, are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Keen Hearing and Smell. The zombie werewolf has advantage on Wisdom (Perception) checks that rely on hearing or smell.

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

Multiattack. (Humanoid or Hybrid Form Only). The zombie werewolf makes two attacks: two with its slam (humanoid form) or one with its bite and one with its claws (hybrid form).

Bite (Wolf or Hybrid Form Only). Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 6 (1d8 + 2) piercing damage. If the target is a humanoid, it must succeed on a DC 12 Constitution saving throw or be cursed with werewolf lycanthropy. If a bite attack kills you, you are brought back to life as a zombie werewolf.

Claws. (Hybrid Form Only). Melee Weapon Attack: +4 to hit, reach 5 ft., one creature. Hit: 7 (2d4 + 2) slashing damage.

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