Another reliable yet powerful solution to import Zimbra mailboxes into Office 365 account is Vartika Zimbra Converter. All you need is to import TGZ file within the tool and software will convert every single mailbox into PST format which you can further import within Office 365 easily.
How to Convert Zimbra to PST Format?
Step 1: Download and launch Zimbra to PST converter.
Step 2: Choose Zimbra TGZ files to convert into PST.
Step 3: Enable desired folders and pick PST as the saving option.
Step 4: Enter a destination path for saving exported files.
Step 5: Start to Zimbra to PST Conversion process.