after a lot of messing around and rolling back drivers and installing new drivers from microsoft and asus (I have a zen ultrabook ), I finally stumbled apon the fix for getting the hdmi output to work!!
the trick is to go to the settings (right flick on the mouse pad) choose devices the go to "second screen" and then while plugging in the hdmi cable at the same time with the mouse choose the connection you want, either duplicate, second screen only, extend or pc screen only.
Apparently the connection is recognized when you click on a choice WHILE plugging in the hdmi cable. I've had 100% success using this method while it would only connect one time out of 20 when just randomly plugging in the hdmi cable. Very strange but it works. Have not found this work around or any other solution for that matter anywhere else. Don't post a lot, but noticed that a lot of people were having problems with this connection. Now if only I could figure out why I have no sound on my youtube videos when going back into my browser having been listening through my bluetooth speakers before and then having them off when reviewing youtube videos. I have sound if I turn the bluetooth speaker back on, but nothing when I turn them off!!?? The only solution I've found is to do a reboot, or reload chrome in desktop version or vice versa relaunch google chrome in windows 8 mode. That will usually get my sound back in youtube videos over my asus zen ultrabooks internal speakers.
I'm sure there are lots of other bugs to be found, but so far these have been really "bugging" me