You can easily export Zimbra to Office 365, then you can download KDETools Zimbra to Office 365 Converter. It is compatible with all versions of Outlook such as 2019, 2016, 2013, 2010, 2007, 2003 and many more. I tried this app myself and got a good result. This application is very easy to use and secure to export your data.
Read More: https://www.kdetools.com/zimbra/office-365.html