From Pathfinder Society Scenario #2-21: In Pursuit of Water, which isn't enabled.

Unkillable Zombie Shambler

CREATURE 0

UNCOMMON MEDIUM EVIL MINDLESS UNDEAD UNHOLY ZOMBIE

A zombie shambler is a slow-moving horror dangerous in larger groups.

A zombie's only desire is to consume the living. Unthinking and ever-shambling harbingers of death, zombies stop only when they're destroyed.

Perception +0; darkvision

Skills Athletics +5

Str +3, Dex -2, Con +2, Int -5, Wis +0, Cha -2

Slow

A zombie is permanently Slowed 1 and can't use reactions.

AC 12; Fort +6, Ref +0, Will +2

HP 20, void healing; Immunities bleed, death effects, disease, paralyzed, poison, unconscious; Weaknesses critical hits 6, vitality 5; Resistances all damage 3

(Zombie) Unkillable

This zombie is nigh unkillable. The zombie loses its weakness to slashing and gains resistance against all damage equal to its level (minimum 3), and it gains weakness equal to twice its level (minimum 6) to critical hits.

Increase the zombie's level by 1 if you give it this ability.

Void Healing

A creature with void healing draws health from void energy rather than vitality energy. It is damaged by vitality damage and is not healed by vitality healing effects. It does not take void damage, and it is healed by void effects that heal undead.

Speed 25 feet

Melee Fist +7 (unarmed), Damage 1d6+3 bludgeoning plus Grab

Melee Jaws +7 (unarmed), Damage 1d8+3 piercing

Requirements The zombie has a creature Grabbed or Restrained.

Grab

Requirements The monster's last action was a successful Strike that lists Grab in its damage entry, or the monster has a creature Grabbed or Restrained

Effect If used after a Strike, the monster attempts to Grapple the creature using the body part it attacked with. This attempt neither applies nor counts toward the creature's multiple attack penalty.

The monster can instead use Grab and choose one creature it's grabbing or restraining with an appendage that has Grab to automatically extend that condition to the end of the monster's next turn.

Pathfinder Society Scenario #2-21: In Pursuit of WaterOGL