I've had networking over USB working for awhile in Cacko and got my best instructions from this thread.
You have to do the NDIS 5 driver stuff on your windows machine first.

Connect To Internet Via Z-usb Cable (xp Bridge)

Previously in pdaxrom/pdaxii13, I was told to use usbnet in a console and that didn't work for me for some reason.

Make the selection in USB settings to "Network" then make the modification below.
Now for the very simple bit that got it working automatically and instantly in pdaxrom/pdaxii13.
Look at step 2.
Step 2 (Perform on Zaurus).
Modify /etc/hotplug/usbdnet.conf



(This make zaurus to automatically obtain an IP Address from a DHCP Server when the USB Cable is connected to the PC)
After the file (usbdnet.conf) is modified, unplug the USB cable from the PC and Re-Connect the USB Cable.
USB networking is now Plug 'N Play smile.gif