The 2.6 kernel uses the g_ether driver for usb networking now. First, make sure to run
modprobe g_ether
ifup usb0

That should bring up your interface on the Z. Note that it is now usb0 and no longer usbd0. Next, follow the instructions on this site to get the windows driver installed:

you may need to remove the old sharp drivers in order to get internet connection sharing to work. I use this setup to get my Z online when I am at work smile.gif
(Just don't tell my IT guys.. wink.gif )