Zooming is just temporary with the two page display mode and I didn't envision it being used except to quickly zoom in and then back out, because you can't turn pages while zoomed in on a page with the two page display mode. With the other modes, MobileSheets saves the zoom and restores that zoom the next time you load the score, and you can turn pages while being zoomed in. If users really want it, I can look into supporting HQ zooming with the two page and half page displays, but it will most likely create a lot of complexity.
Mike
Mike