Zooming in on photos works badly. You need to touched your screen by two fingers perfectly at the exact same moment. If you do not hit the timing perfectly, then minimize the photo and having fun again. You should be able to press on the photo with one finger first, and then when you put your second finger down you can zoom in, regardless of when exactly you use your second finger. Of course I know you can double-click on a photo, but sometimes it's better to do a pinch to zoom.