Only one of the internal USB ports supports using the ZU130 disk (and possibly booting from it).
See the Product Guide, it's all there.
You can plug in the Z-U130 on a 'normal' internal USB connector. One of my fellow students is using one Z-U130 on a 'normal' internal USB connector and is booting from it.
My question is: Can I plug in two Z-U130 to only one internal USB connector?