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.

Morningstar. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 7 (1d8 + 2) piercing damage and 7 (1d8 + 2) bludgeoning damage.

Shield Bash. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 4 (1d4 + 2) bludgeoning damage. The target must make a DC 13 Dexterity (Acrobatics) or Strength (Athletics) or suffers one of the following: The target is knocked prone or the target is pushed 5 ft away from the zombie knight.

 Multi-Attack: The zombie knight will make two attacks, the first with its Morningstar followed by a Shield Bash.