"GPS||Run;C:\Program Files\iGZoom\iGZoom.exe" (assuming thats where your igzoom is)

Change your exit gps to this

"RunQ;C:\Program Files\Close Zoom\Close Zoom.exe||Exit"

and lastly change your close gps button to this

"RunQ;C:\Program Files\Close Zoom\Close Zoom.exe||Close"

.. and there.. zoom tool turns on and off when you want it to