Always use two fingers to zoom in and out. On the emulator, you need to press the select key so that two fingers appear on the screen of the emulated screen (I think that this is the Alt key, but I use the PC keyboard on my Mac, so it may differ on a real Mac keyboard)
Regarding the execution of the procedure, you need to set the region on mapkit. using the method of setRegionyour object MKMapKit.
Make sure that you are within limits, although this can lead to failure if not. (i.e. -180 long