Echolocation. The bat can’t use its blindsight while deafened.
Keen Hearing. The bat has advantage on Wisdom (Perception) checks that rely on hearing.
Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one creature. Hit: 5 (1d6 + 2) piercing damage.
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.
Slam. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 4 (1d6 + 1) bludgeoning damage.
Severed Limb. The first time a zombie takes slashing damage, in severs a limb. That limb animates and can also attack as an independent creature. It has the same stats as the zombie with the following changes: It has a speed of 10 ft. and 10 hit points.
Slam. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 4 (1d6 + 1) bludgeoning damage.
Claw. Melee Weapon Attack (severed limb only): +3 to hit, reach 5 ft., one target. Hit: 3 (1d4 + 1) slashing damage.