Hi
Download the free (Windows) tool called dawn5 from:
Dawn
If its an address book, it can read it, and save it, and import it and export it and and...
For Thunderbird, open the wizard, then file->open from file... Select type Mozilla/Netscape and browse into the user's Thunderbird profile directory. Open the .mab file (default one is abook.mab). Repeat this for other addressbooks if you want to consolidate books. Do the same for Outlook and Outlook express and whatever else the person uses.
Then, once you've collected everything you want, do File->save as file... and choose csv file. Then import that into zimbra
