Dog uses his round 10 reaction to cast force as a cantrip, since he was hit by an attack. Does the woman appear to be holding anything: scepter, book, weapon, wand, etc? If so, Dog will make the affect be to knock the object out of her hands. If she's not holding anything, he'll levitate a stone within 5 feet of her to hit her for 2 damage.

(Does the statue in the middle look like a larger/stonier/healthier version of the woman in crimson robes?)

(And do we hear/see any more zombies coming from behind them?)

For round 11, he'll attack Z15 with green flame blade Attack: 14 Damage: 11 and have the 2 fire damage jump to Z21.

There is an uncanny resemblance. No more zombies are visible or can be heard. And Z21 is more than 5 feet away from your target, I'm afraid. 

M DEX(13) check: 2

Dog lifts the stone that he just struck the woman with and flings it at her again, although with much less force than before. He then slashes at the zombie in front of him, spilling intestines onto the ground. The zombie looks unfazed.

On Z16 Attack: 20 Damage: 5 BA Attack: 19 Damage: 5

(That's fine about Z21, but what about Z16 right next to it?)

(Do these zombies taking damage now seem.... less fazed than the zombies we've just been damaging?)

(These zombies are unflappable! Z16 is about 10 feet away. I know, the scaling is a bit zoomed back on this map. It is a big plaza!)

Z16 CON(10) check: 19

Z16 CON(10) check: 11

Twice Feytok hacks at the zombie with his battleaxe and carves chunks of the corpse off in the act. But it appears to be nothing vital and the creature continues on.

Tock continues with his plan, but shouts first, "Which way is the Serpent Valley?". Then he takes another shot at Z17 and moves east.

Attack: 21 Damage: 7

Keyrie will move up 30ft, then move the moonbeam on top of the leader of the zombies. 
Con Save of 13 for half damage: 9

Tock's arrow is true, striking the zombie in its pelvis.

The woman begins to sizzle and smoke in Keyrie's moonbeam.

(Gash and Lucien are up next.)

Gash shoots another fire bolt at Z17

Attack: 14 Damage: 5

Gash's fire bolt scorches the zombie, leaving it a shambling, black husk of a corpse. It does not fall, however.

(Lucien is up.)

Seeing Tock out in the open alone, Lucien charges north and east, coming around the statue to target Z17 with Toll the Dead

Z17 WIS(14) check: 8

The Zombie takes 5 damage.

Z17 CON(10) check: 13

Parts of the zombies torso, arms and legs dissolve under Lucien's spell. Glimpses of its skeleton are visible everywhere but it continues to walk.

Z15 swings its arms like clubs at Dog.

Attack: 10 Damage: 6

And Z16 does the same to Feytok.

Attack: 22 Damage: 3

At the same time, the woman strolls up to Dog and Feytok between the two zombies that are keeping them busy and scratches at (2) Feytok.

Attack: 6 Damage: Unable to parse dice roll. bludgeoning and 10 necrotic damage.

(advantage attack roll that I forgot to apply: 22. Yikes! Additional bludgeoning damage: 9. Additional necrotic damage: 11. Total damage after resistances is 35 HP!)

Feytok CON(12) check: 8 . (Feytok is NOT cursed.)

She then turns to Dog and glares at him in a sweet but menacing way. "Go," she says, simply.

Dog WIS(11) check: 8 (Dog is frightened)

Oh! I forgot Moonbeam damage check. CON(13) check: 17 or take 9 damage, half on a success.

(Everyone may take their round 12 turns.)

Gash takes out a stick of butter and chomp a bite out of it chews it up and blows it out of his mouth casting Grease on the woman

Z15 DEX(12) check:  2

Z16 DEX(12) check:  0

Woman DEX(12) check:  3

All three of the undead fall unceremoniously on their backs and faces and are now prone.

Tock yells, "Lucien, Gash, I've got this, help the others!"

Then he takes another shot at Z17: Attack: 10 Damage: 11

.. and runs (movement + BA: Dash) towards the eastern entrance to the plaza, hopefully having enough distance to turn the corner and hide behind it.

 "Ouch.  My turn" (at the woman) Attack: 19 Damage: 9 BA Attack: 18 Damage: 14

Z17 CON(16) check: 10

Tock's bolt finds its mark, finally bringing the zombie to an end.

At the same time, Feytok swings at the prone woman and strikes the ground, but in a wild surge of rage, strikes again, this time slashing across her back.

Dog shrinks away from the woman to the left, deeply affected by her command to leave, and checks the exits. He sees a zombie on the ground struggling to get up and he steels himself and finds he isn't afraid of this one like he is the woman and so he he hits the prone Z15 with green flame blade with the 2 damage going to the woman: Attack: 15 Damage: 5

Keyrie will move the moonbeam on top of the woman again maximizing the number of zombies affected. Three if possible if not then just two.
Con save 13 for half damage: 3

"How is everyone doing? Does anyone need a little pick me up via spell?"

Z15 CON(12) check: 9 (oops, I didn't need this for Z15!)

Dog stabs the zombie in the back. The green flame jumps to the woman, scorching her arm and leg (no, it doesn't ignite the grease. ;)

Keyrie shifts her moonbeam to the woman and it barely touches the flailing arms and legs of the adjacent zombies.

Z15 CON(13) check: 9

Z16 CON(13) check: 16

Woman CON(13) check: 10

Keyrie's spell is only able to damage each zombie minimally. However, this is enough to still one of the corpses (Z16 is dead).

(Lucien is up next.)