I do not know of anything that eats nudis, sorry. :( There might be a chance that some of the wrasses would, but anything that would eat them I think would also eat your other good members of the CUC.
Do you know what kind of nudis they are? Have you posted a picture here yet?
You have to repeatedly dip the zoas in coral dip to kill the adult nudis, and pick off the egg sacs with tweezers. You have to keep doing this until there are none left.
They can be extremely hard to see when their on the zoo's. They'll change their color to perfectly match to corals their feeding on. And they can be pretty dang small too, and that doesn't help. But after you've spotted one or two, then you'll be able to spot them easier.