Enhanced Undead Fortitude. If damage reduces the creature to 0 hit points, it must make a Constitution saving throw with a DC of 3 - 2 + the damage taken, unless the damage is radiant or a critical hit. On a success, the zombie drops to 5 hit point instead.

Unstable gaunt. At the end of this creatures turn choose the closest player (choose randomly if there are several) and Zombie of Rotting Mail moves 5 ft in their direction and attack with slam at disadvantage if within range.

Garbled tonged. to understand this undead a creature requires a wis or int score of 14 or higher to understand or a DC 14 wis or int roll

Rotten Mail. If any creature try's to grapple , restrain or otherwise contact Zombie of Rotting Mail they will take 2 (1d4) poison and 2 (1d4) necrotic and suffer a -1 to Str saving throws until the end of turn.

Rotting resistance. this creature is immune to nonmagical poisons and takes 1 less (minimum of 1) damage from magical poisons ,Necrotic and non magical bludgeoning piercing and slashing damage.

Slam. melee weapon attack: +4 to hit ,reach 5 ft., one target. Hit: 5 (1d6 +2) bludgeoning damage and must make a DC 13 Con check or take an additional 1 (1d4 -2 with minimum of 1) poison and 1  (1d4 -1) necrotic damage

Rotting Grasp. melee weapon attack: +4 to hit, reach 5 ft., one target. Hit : 5 (1d6+2) bludgeoning damage and if large or smaller must make a DC 15 Str check or be restrained and take an additional 2 (1d4) poison and 2 (1d4) necrotic and suffer a -1 to Str saving throws until the end of turn every turn while restrained. While restraining a creature Zombie of Rotting Mail can not use this action again and suffers from disadvantage using slam. If enhanced undead fortitude comes into effect while restraining a creature they are released and gain an attack of opportunity on Zombie of Rotting Mail.