I would like to suggest you secure software Zimbra Converter software to migrate Zimbra file to Outlook PST. This software convert Zimbra TGZ file to multiple file formats such as PST, EML, EMLX, HTML, OLM, NSF, MBOX, and etc. This software also directly migrate Zimbra file to Exchange Server and Office 365 account.
Read more:
https://www.kdetools.com/zimbra/