Keen Smell. The zombie has advantage on Wisdom (Perception) checks that rely on smell.

Regeneration. The troll regains 10 hit points at the start of its turn. If the troll takes acid or fire damage, this trait doesn't function at the start of the troll's next turn. The troll dies only if it starts its turn with 0 hit points and doesn't regenerate.

Undead Fortitude. If damage reduces the troll to 0 hit points, it must make a Constitiution saving throw with a DC of 5 + the damage taken, unless the damage is fire, acid, or from a critical hit. On a success, the troll drops to 1 hit point instead.

Turn Immunity. The troll is immune to effects that turn undead.

Multiattack. The troll makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 7 (1d6 + 4) piercing damage.

Claw. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) slashing damage.