Hello everyone,
I too was in the same boat until I tried something silly out of frustration. I was using a microHDMI-to-HDMI adapter to connect to my zenbook. After trying unsuccessfully to make the external display work for about 30 min or so , I pushed the adapter with more force and to my surprise it seemed to do the trick. Looks like the micro HDMI port on the zenbook requires very tight fit. May be this is a build issue with the zenbooks.
My setup for completeness-
Bought zenbook with Windows 7 and later upgraded to Win 8 Pro. I'm using cheap HDMI cable and a microHDMI-to-HDMI adapter (from monoprice) to connect the laptop to my Sony HDTV.
HTH.