I have a Z9 Plus, and the front I/O panel only has usb 2.0 ports, and the Z9 U3 has both usb 3.0 and 2.0. I am going to upgrade my motherboard to be compatible to usb 3.0. Would it be possible to find the front I/O panel of a Z9 U3 and put it into a Z9 Plus?
The real problem there is that the front panel is the most likely part to break so finding one in good condition, not on a case is the trick. Zalman does not seem to have case parts available although you might contact them and inquire about the possible replacement of your front panel. Of course I would simply purchase a 5 1/4" SUB 3.0 front panel adapter like this http://www.newegg.com/Product/Product.aspx?Item=N82E168... for $13 personally
Hope it helps