Swarm. A zombie gains a +1 bonus to attacks for every other zombie the is within it's target melee range.
Aim for the head. if a creature attacks a zombie's head and the attack hits, the damage for that attack is doubled.
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.
This effect does not occur if the Zombies head has been destroyed.
Grab & Bite (Recharge 5-6). if a zombie succeed on a grapple, it can Immediately attempt to use a bite attack on the grappled creature. If the zombie fails the grapple, it cannot us this ability on the same creature on it's next turn.