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.

Frenzy, If the Zombie Soldier has its Hit points (17) reduced to half or lower it drops its halbeard entering into a mindless rage were it gains the following benefits.
It gains 10 temporary hit points.
It speed increases by +10ft 
and in addiction it have advantage on constitution saving throws.

Multiattack: The Zombie soldier can attack twice whit its slam attack if he loses its halbeard, but it can only make one attack whit its halbeard.

Slam: Melee weapon attack +5 to hit, 5ft range, one target for 1d6+3. bludgening damage

halbeard: Melee weapon attack +5 to hit, 10ft range, one target for 1d10+3 slashing damage

Rush: The Zombie Soldier can take a Dash action as a bonus action