with mild cases, good water quality and excellent flow can make it go away IME without treatment.
If the pox is very severe, I would ask you to re-evaluate the statement as to whether or not the rock can be removed from the tank for treatment. Every rock can be removed somehow. Its about how bad you want to save the zoas, as well as prevent it from spreading ot other colonies.
If you want to tackle this little project and save those polyps, but are unsure of how, or uneasy of how the safest and easiest way to do it is.......ask away. There are definitely right and wrong ways to do it for both safety and time, depending on your system.