Have you tried my demo? I posted it here a few times:
https://www.dropbox.com/s/p40ibb75m9g8z8j/ZoomTouch.capx?dl=0
Run in Chrome, it may not work very well in Firefox due to some bug with touches getting "stuck".
Very nice DOP, thanks a lot for this. Is it possible to zoom through pinch out/in touch only one blue box instead of whole layout?