On the 5D2 and 7D, when you review an image you've taken on the LCD, to zoom in or out you simply just had to press either of the top-right thumb buttons on the camera. However, now on the 5D3, you have to first press the magnification button under your left thumb, then turn the main dial to zoom in or out. Essentially they added a step. I've been going through the manual, but I can't find a way to customize the buttons to revert back to the old way. Is there no way to do that???