fighting orks, 4 zoanthrropes w/nerathrope or 2 crushing claw and talon carnifex?

Carnifexes could kill some boys in a Mob but then die to the nobs PK. You're better of with the zoanthropes who can Cast a bunch of powers around. Keep them out of sight of lootas and shootaboyz since their overwhelming firepower will make life short for them.
High I and lots is the way to go against orks.

as an ork player i hate seeing the twin linked devourer carnafex.

if your opponent uses trukks your zoanthropes will have a hard time hiding from them, providing your opponent knows and understands the target priorities for orks against nids.

biovores with there don't have to see you blast templates are also very hurtful as well

Oh as an ork player I hate to see the dakka fex. The crushing claws and talons aren't that worrisome to orks. Zoanthorpe if it is in a bunker or building could be a problem but usually die pretty easy to loota fire.