Screen zooming has three different settings for how the zoomed portion of the screen will follow the mouse cursor, as listed in the Accessibility system preferences / Zoom / More Options. The only one that works with touch and our driver is "Only when the pointer reaches an edge" due to the fact that synthetic mouse events will go to the correct position on the zoomed screen, so it can be used with the driver’s mouse emulation or UPDD Gestures interface.
The other screen zooming settings, "Continuously with pointer" and "So the pointer is at or near the center of the screen" both move the screen image every time the cursor is moved, so whenever the user touches the screen, the image will jump chaotically, hence is not suitable for touch.
OS X also supports an alternative "picture in picture" zoom, and that's also works with the driver, either by itself or with Gestures.
It may be possibility to determine how the screen is zoomed and support the other two settings but it is unlikely that those zooming methods will be used with touch so we have not pursued this support.