See what the 5500 can be sync'ed with, then try to get the data into that format would be my advice.
Outlook used to work for me, so I'd try to get your ZR5800 into Outlook somehow (via Act, etc.),
Then go from there.
Otherwise it may not be too difficult (if you have some programming experience) to write a script which will turn your ZR5800 data into a load of vCards etc.
Si