As the door crashes in, the zombies awaken and move into combat with the party.

Initiative order (AC is 8, but I'll need to roll a check when they reach 0 hp):

1. Galben
2. Zombie B
3. Zombie C
4. OldMan
5. Thallan
6. Zombie A
7. Zombie D
8. Bearkiller
9. Jake
10. Tubard
11. Regula
12. Zombie E

(Galben moves around the statue in front of Regula and looks through the door seeing Zombie A and fires and arrow striking the undead in the shoulder. It looks at the arrow and starts walking forward. 4+7=11, Hits. Damage 6+3=9 piercing damage)

(Galben them moves between OldMan and Regula to make room for others to engage in the fight)

As Galben hits Zombie A, you see a puff of ash emanate from around it. Since no one is near it, nothing further happens.

Zombie B advances on the door and attempts to slam against it but it loses momentum on the advance and fails to deal any damage to the door.

Zombie C advances on Tubard in the doorway, attempting to slam into him. The zombie trips over a slightly elevated paving stone on the floor and more stumbles into Tubard, causing no damage (9 to hit). Tubard pushes the Zombie back upright after it makes contact.

OldMan casts Chill Touch on Zombie A  14+6 +20 hit does 6 pts necrotic damage.  Zombie A's attack is at disadvantage until the end of the next round.

Thallan, being low on HP uses his action to drink one of the healing potions he is carrying (1+1+2= 4 HP), increasing his HP to 9.

Zombie A attempts to slam into Tubard and connect (20 with disadvantage), causing 2 bludgeoning damage. Zombie D slams the door to its room, splintering the wood in a cloud of dust. It moves toward The main doorway, expending it’s movement and ending 5’ south of Zombie C’s starting point. 

(Bearkiller moves 10 ft behind Tubard and throws a dagger at Zombie C and strikes it in the side. Attack roll 15+5=20. Damage Roll 1+3= 4 piercing damage)

(Bearkiller then uses the rest of his movement to move back where he was)

Jake runs behind OldMan's starting point.  Seeing zombie A inside the room, Jake casts sacred flame and if he connects, does 4 damage. 

Tubard rages and rushes towards Zombie C and swings his great axe violently (13+5+1!=19 to hit) and deals (11+3+2 rage+1 mod= 17!) with a wallop Tubard decimates the zombie. “Guess I was saving my power for these zombies”

As Bearkiller's dagger strikes Zombie C, it emits a puff of ash, and Tubard needs to make a Con Save against a DC 10 or gain disadvantage on attack rolls, saving throws, and ability checks for 1 minute (going forward from this point).

Jake's sacred flame connects with Zombie A causing 4 damage.

Regula downs a healing potion regaining 7 hp and runs into the fray, engaging Zombie A in melee to its west.

Zombie E lurches to life and moves through the cratered door and into the main room, just north of Zombie D advancing on the party waiting outside.

(Galben moves out from behind the statue and takes aim at Zombie A releasing the arrow and striking it in the stomach. Attack roll 5+7=12, hit. Damage roll 2+3+8 (Collossus Slayer)= 13 piercing damage.)

(Galben the moves out of Oldman's way bak behind the statue)

"Let's see what you got Gary!"

(20!+4=24 constitution saving throw)

Zombie A stumbles for a moment after being struck by Galben looking like it might maintain the strength to continue fighting but quickly collapses in a pile of ash and bone.

Zombie B slams the door in its room, making contact and splintering the door considerably; however, the door remains (mostly) in tact and will require an additional hit from the Zombie to break.

Zombie C slams Tubard but is not able to muster enough momentum in close melee combat to land a clean strike (12 to hit).

Bearkiller is up with Jake on deck.

(Bear killer takes his other dagger and throws it at Zombie C from about 15 ft away. Attack Roll Nat. 1, His throw goes wayward and hits Tubard for 3+3=6 damage)

"Sorry friend, I'm still working on this range attack thing" 

Jake moves up, just south of Thallan. From there he can see through the open door zombie E. Jake casts Sacred Flame with the knowledge that Ilmater will smite the evil zombie for 1 radiant damage.

Sorry all - totally messed up the combat order! OldMan and Thallan should have been up next, so go ahead and take your turns.

Zombie E saved without issue, Jake (nat 20). Ilmater expects greater penance from you, apparently.

(OldMan casts Chill Touch at Zombie C and hits. Attack roll 13+6= 19, Damage roll 3= 3 necrotic damage)

Zombie C collapses under OldMan attacks and crumples to the ground presumably dead. A moment later, it reanimates with 1 hp.

(Thallan moves in next to Tubard with his rapier drawn and swings at the undead, Attack roll 10+6= 16, hit. Damage roll 1+6= 7  piercing damage)

"That should do it...hopefully"

As Thallan's rapier pierces through the fetid, rotting flesh, the Zombie stumbles momentarily and collapses in a pile of ash.

Zombie D ambles out the front door and into melee combat with Regula, attempting to slam him but losing momentum due to the distance he had to come (9 to hit).

Tubard is up with Regula on deck.