I don't believe that you can show a zoomify on top of a loaded pano. You can click on the curtain and then load the zoomify image... but it will replace the pano.
Zitat
I do not mind the hotspot with link to another URL !
You can use the openurl action to open a new window / tab for the zoomify file..
i agree you would need to open an ifram or something inside the html window and i dont think flash html supports that. openurl externally is the only thing i can think of also.
How about using a Lightbox to show the other pano ? since Krpano supports JS calls I think it could work, I have never tried it, but it seems it could work.