I can use my 4 slot 12 in 1 card reader to use CF cards on my Zaurus, but I'm running Cacko and I think you may need a USB module for it to mount automatically.
My 12 in 1 card reader only shows the CF slot in the filebrowser on my Z.
I think it only mounts the first slot, since the CF slot is the first one.
(It doesn't work with the SD slot, which is the 3rd slot).
I also have a single slot 5 in 1 reader that works in Cacko with SD/MMC cards.
If your'e using Sharp rom, you may need to use the USB modules in the Cacko feed.
I have this installed in Cacko Lite:
get it here:http://web.mol.ru/~zaurus/feed/
This doesn't solve the problem of the Zaurus not reading the microdrive directly in the CF slot, but it should work with a card reader hooked up to USB, unless the microdrive pulls more than 3.3 volts.
The Zaurus USB host only works with devices at or under 3.3 volts.
A desktop PC has 5 volts at the USB port.
If any of the above is incorrect, someone else please step in and correct me.