The Zaurus can already sync to Yahoo!
You need to download "Intellisync for Yahoo!" from either the Calendar or Address Book on Yahoo!. When you run this version of Intellisync, if you have the Zaurus Intellisync already installed, you will see Zaurus as a "translator" when you select a PIM app, then click the "Choose" button.
Note that Yahoo! does not show up as an option in the Zaurus version of Intellisync.