instructions on the pdaxrom site are a bit out of date, so i updated them for an install on a c760, should be easy enough to adapt to your own model.
Extract the 3 files - initrd.bin tools.tar updater.sh - to the root of your CF or SD/MMC card.
Make sure the Zaurus isn't plugged into AC power.
Remove battery for at least 5 seconds.
Replace battery (replace battery cover, lock cover), plug in AC power.
Press and hold the "OK" button on the keyboard.
Turn the power on, you should see the Japanese service menu.
Select option 4 (flash/update).
You then have four options (1. USB, 2. CF, 3. SD, 4. Back)
press the button on the left with the 'Y' in it
Choose either option 2 or 3, depending on which media you put the files on.
the pdaxrom installer is launched.
choose option 3 NAND Flash Utils
choose option 3 fix sharp loader NAND 64MB limit (sl-c760/c860 only)
fix is applied, then you reboot
go through options again
chose option 1 resize root partition
choose option 1 install new rom
the rom is flashed
reboot the z
at login prompt, log in as root
then calibrate the touchscreen