We can create contact group in the Zimbra from the galsync account, to create the group contact you can follow the given below instruction.
Login to the galsync account to create the group contact.
User Name : firstname.lastname@example.org
Password : *****
Add a name to the contact group.
Adding contacts in the contact group, one can also add external email address here.
These are the very simple steps one can create an contact group in galsync or even in any ones personal email address, the procedure us the same.