If you have TGZ files and it is difficult to move them around on your own. You can get help with Vartika TGZ to PST Converter app for free. This way you can change multiple Zimbra files in Outlook PST, EML, EMLX, MBOX and MSG. Download the trial version and see how it works. With this demo version you can migrate the first 10 items per folder.

Know more info- Zimbra to PST Converter | Zimbra TGZ to PST | Zimbra to Outlook