Here's what works for me to disassemble the CZ75.
I hold the unloaded gun in my right hand with the slide "pinched" and held in position (disassembly marks aligned) with my right hand.
The fingers of the right hand are over the top of the slide with the thumb around the backstrap. Then squeeze until the marks are lined up.
Next I place the front of the triggerguard against the web of my left hand and put the thumb side of the top joint of my left index finger against the slide stop "button" on the right side of the pistol and my left thumb on the left side of the pistol and squeeze the thumb and finger together.
The part of my left index finger contacting the slide stop "button" is the side of the last finger joint--basically the bone on the side of the topmost knuckle. That means there isn't much give and it's possible to put enough pressure on it to pop it out.
I wouldn't want to do it all day long, because eventually that knuckle will get pretty sore. But then I've never been in a situation where I needed to field strip CZ-75 pistols all day long!