wmctrl does not move a zenity window in a bash script unless it is first deactivated. By deactivated and then activated zenity you can change the position of the window. For example add the following lines before the zenity command (z-name is the name of the zenity window):

 (
sleep 0,5
wmctrl -a Firefox
wmctrl -a z-name
wmctrl -r z-name -e 0,2000,400,-1,-1
) &