Best way is with a sight pusher. If you don't have one or access to one...
Put it on a padded surface (on top of a folded towel).
Use a big brass punch or hardwood dowel, and a HEAVY HAMMER and carefully hit the rear sight in the direction required.
Start light and then hit it harder and harder until you get results.
Be careful where you place the punch,as you can chip the paint on the slide. (Been there, done that.) Go slowly. (I didn't, the first time.)
With some CZs, you'd swear the rear sights are WELDED in place.
