Can't interact with google map zoomcontrol with a .png overlay?

Hi all,

Here’s an example:
renjeroute.nl/gadgets/hyvesgadget.php?routeID=110507B2VU

I have used this class http://blog.mosessupposes.com/?p=40, so the transparent .png is clickable. But now the map zoom control can’t be used.

Any tips