I just bought a Zbook 14 and running Windows 8.1 x64. When the computer resumes/wakes from sleep mode the screen is just black and I have to fore a restart by pressing and hold the power button.
Currently I am having problem with the AMD video drivers, and it seems to be related (update below), see this thread: http://h30434.www3.hp.com/t5/Notebook-Display-and-Video/Zbook-14-AMD-Firepro-drivers-problem/td-p/3878422
Update 1:
If I disable the AMD card in Device Manager the sleep works but the sleep is not indicating by the pulsing light on the power button (minor but good to know).
When I resume from sleep the Intel card in the Device Manager says:
Windows has stopped this device because it has reported problems. (Code 43)
And the brightness control does no longer work.