The finish on the older CZ-75s and even the transitional models is far different than the current polycoat finish, which is very hardy.
I'd suggest you get a can (not spray bottle) of auto paint remover from an auto parts store. That's about the most powerful stuff you can find that won't eat YOU along with the gun and finish. Try it on a part of the frame under the grips. If it works, get an old paint brush, and paint the gun with that stuff, removing the bubbled up finish periodically with paper towels, and repeat until the finish is off. (If there's an auto body shop nearby, you might talk to them to see what they'd suggest for getting that finish off. They have to strip, sometimes, too.)
Be warned: CZ applies a manganese phosphate finish under the polycoat, and the finish itself, when all is removed, won't be pretty and without blemishes. Some polishing will be in order -- and if you're going to have it refinished, your best bet is to let the refinisher do ALL the work.