Try any professional software such as Zimbra to Gmail Converter to convert Zimbra TGZ file to Gmail and various types of file formats such as EML, EMLX, HTML, PDF, MBOX, NSF, OLM, etc. The tool supports all the latest versions of Windows, such as Windows 10, 8, 7, 2000, Vista, etc. The tool also directly transfers Zimbra to Gmail, G Suite, Google Drive, etc. The software saves email metadata and folder structure in the process transformations.
More information: https://www.kdetools.com/blog/how-to-import-zimbra-to-gmail.html