I would like to suggest commercial solution like Zimbra to Office 365 Converter. This tool import Zimbra items such as emails, contacts, journals, notes, and etc. This application import Zimbra to Office 365 and multiple file-formats including PST, EML, MSG, EMLX, vCard, vCal, an etc.

Read more: https://www.kdetools.com/blog/migrate-zimbra-to-office-365-directly.html