Migration process of the Zimbra TGZ file to Outlook 365 takes a long route. First of all, you have to Convert Zimbra Mailbox data into TGZ files. Select the Files and click on them > Save them as TGZ, For migration of TGZ file to Outlook 365 you have to convert it PST. Download the WebbyAcad Zimbra migrator tool > add your TGZ files here > preview the file > select the file format PST > Set the file saving location and press the export button.

After these things open the outlook365 > Create a new Outlook file > drag or drop the converted PST files.

For more details:- https://www.webbyacad.net/