Excuse my ignorance, but other than pinch to zoom, what is 2 and 3 finger multi touch being used for on the iphone because if its not being used, the solution seems simple. The best answer is to make a section in setings where you can see what your multitouch options are and let you set what does what the same way that you can on your Mac.
You can tap with three fingers and then drag to zoom into the screen like a cntrl+scroll on the mac. (That is, if you allow it in system prefs.)
If you meant that (when you mentioned "zoom") already, sorry.