I'm not familiar with the z600 but I just note the wire coloring at the switch, at worst you just follow the wires down to the connector.
Solid White is often the common or ground wire that all the switches will use.
Repeating this for USB can be done but you will need to know what you are doing to tell which wire is which pin if HP didn't use standard wiring there too.
Unless you have a z600 case/psu I would suggest you sell the z600 and start with a Supermicro X8DTi-F (1 x pci x16) or X8DAI if want on-board audio or the X8DTG-QF if you want 4 pci-x16 slots and an "unsupported" quad sli gpu monster.
Here's my "i5-6400 build" that morphed into a X8DTi-F Dual x5680, 48gb ddr3, 240gb pci-ssd, gtx 760 beast
And when everyone claims you can't watercool Supermicro server mobo's, or any server mobo (the party line is to water cooling is "not compatible") Nope, it's a pretty cheap & simple work around, and if this doesn't convince you that water cooled servers are real..