If you are searching for useful tool to convert Zimbra file to Office 365, then you can use Zimbra to Office 365 Converter.
Some features are:
• This application convert Zimbra file to Office 365 and Exchange Server account.
• This tool also convert Zimbra TGZ contacts and calendar to Office 365 account.
• Convert Zimbra TGZ to numerous file formats for example PST, EML, EMLX, HTML, OLM, NSF, MBOX, and other file formats.
• This application shows free preview of the data prior to the conversion process.

Read more: https://www.kdetools.com/zimbra/office-365/