Undead Nature. A zombie doesn't require air, food, drink, or sleep.

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.

Two Heads. The two-headed crocodile has advantage on Wisdom (Perception) checks and on saving throws against being blinded, charmed, deafened, frightened, stunned, and knocked unconscious.

Wakeful. When one of the crocodile’s heads is asleep, its other head is awake.

Multiattack. The two-headed crocodile makes two attacks with its bite.

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 7 (1d10 + 2) piercing damage, and the target is grappled (escape DC 12). Until this grapple ends, the target is restrained, and that head of the crocodile can’t bite another target.