Looks like a pretty solid Zilla list.
What is the role of the Gaunts? Are they attacking, or just getting in the way?
+1
WS is cheaper than Toxic Miasma
I really don't think a single Psy Scr will have much effect. Getting a 2+ save however... go with the Warp Field. You may want
TS.
Think about going with a smaller retinue. It is easier to infiltrate and hide with a smaller retinue. Personal play style, but something to think about. Acid Maw is rarely worth it, for any model. Think about feeder tendrils, if any of the gaunts are going to support.
10 is pretty small brood for gaunts. Unless they are only meant to slow folks down.
Gargs are awesome.
Zoan: If you want synapse, you have to pay for it.
Remember, your fexes can always shoot. And have a LD10 for moving. Again, I don't think a single PsyScr will do much for you.
EC is better than Exoskeleton, Chitin, and Regen. You are better off with the better save.
You may develop synapse issues. You have 3, but one has infiltrated, and one is flying away. That only leaves you one, and it doesn't fleet. Not insurmountable, but something to watch out for.
OTOH, drop the Zoan, and they will 'run away' right into the enemy.
Most of your power is slow, so be careful about hanging your
HT off by itself, especially with only a 3+ save.