You can try our software Zimbra to Gmail Converter tool to convert Zimbra to Gmail. Some basic features are:
• This commercial tool easily convert Zimbra to Gmail account and different file formats such as PST, MBOX, EML, EMLX, HTML, PDF, etc.
• This software directly convert Zimbra TGZ file to Gmail, G Suite, and Google Drive etc.
• This tool is also supports all versions of MS Outlook & Windows.
Read more: https://www.kdetools.com/zimbra/gmail/