Both of them maybe have same problem for the cable management. From the review: NZXT "There is around 15 mm of space below the mainboard tray, which may not be enough if you fill the chassis to the rim with hardware."
http://www.techpowerup.com/reviews/NZXT/Source_210_Elite/4.html
ZALMAN ( I found the review on Zalman Z9 Plus that is as same as the Zalman Z9 U3. I did check) " At first, we tried using the provided zip ties to reduce the mess and bind the cables together, but we were unable to fit the side panel on. Even with the cables spread out, the panel bends a little. Cable management will be even more difficult for those running large RAID/SAS setups on their hard drives, or multi GPU configurations like SLI or CrossFire."
http://www.bjorn3d.com/2011/04/zalman-z9-plus-mid-tower-case
But one thing I like the Zalman Z9 U3, it has the 2-channel fan controller and external LED temperature display, also the CPU 12V extension cable.
So you have to make your own decitions. Sorry. I am out.