Tzentch doomstack against Lizardmens?

So I have to destroy 2 or even 3 lizards factions (I play with victory overhaul) and everyone is busy with wars so can't force anyone really to do the job for me. I ran quite balanced army but it is not doing that great in autoresolve (some chaos knights, flamers, pink horrors, bird, souls grinder and beasts) and even fighting 2-3 armies manually I can't lose some "man" cuz they are running their own doomstacks...

Shoukd I focus on soul grinders or just birds or there is no counter for Lizardmens? Rest of factions are busy with rats and chaos...