how to zoom in powerpoint presentation mode?

I use powerpoint for mac a lot and like to zoom during a presentation by holding the control button and slide two fingers across the trackpad, but that only seems to work if display mirroring is enabled. If it's running the two monitors side by side (presentation view mode), and I try to zoom, it zooms way off center or way off where the mouse cursor is. Does anyone know how to zoom the right way when in presentation mode?

Thanks.