Here is a pair of scripts that I created to batch convert addressbook information from squirrelmail to zimbra.
I have only tested this on my versions
squirrelmail 1.4.19 squirrelmail
Hopefully this will be of some use for other people and probably for other migrations with some adaptations. The email itself we imported with imap-to-imap
On the squirrelmail side, theres a php script that connects to the squirrelmail database, it creates a csv file for every address book.
Then on the zimbra side, there is a bash script which loops this directory and executes the appropriate import command, which at this version is
"zmmailbox -z -m email@example.com pru /Contacts mycsv.csv"
The bash script must be executed as 'zimbra' user : do
'su - zimbra'