I would like to suggest professional software like KDETools Zimbra to PST Converter.
• Zimbra to PST converter tool directly import Zimbra files to Gmail, G Suit, Google Drive and etc.
• Support multiple file formats such as OLM, MBOX, MSG, EML, EMLX, PDF, HTML, etc.
• This software also import Zimbra file to Office 365 mailbox and Exchange server this two format use for online Conversion.
Read More: https://www.kdetools.com/zimbra/
Well, according to the majority of Zimbra users, the best option for TGZ to PST conversion without any data loss is by using an automated tool. SameTools' TGZ to PST Converter Software is one of the most reliable applications for this purpose. It is capable of converting unlimited Zimbra mailbox items, including inaccessible data. The software has the ability to convert all Lotus Notes information into the original file format, such as PST, HTML, MSG, EML, EMLX, etc. For conversion, install its free demo version.