What to do with 4 zetas now that I don't care anymore.

CLS lead zeta really makes a difference in arena. Also Chewie zeta worth it. You already have zzR2, you could run them with Ebb & Flow on Thrawn too. I was full Empire before and I'm now running Rebels and I have the 3 zeta on CLS, which imo worth it.
I also plan to run zVisas because I think she's underrated and can fit in this CLS team with R2, Chewie and Han.

I won't zeta BB-8 since you don't have Rey and as you told your Phoenix are strong enough.