Here are the general steps to follow:

Prepare your Zimbra account: Before you can begin migrating your data, you need to make sure your Zimbra account is set up properly. This includes verifying that all data is backed up and that you have administrative access to the account.

Set up your Office 365 account: You'll need to create an account in Office 365 if you don't already have one. This involves setting up a domain, creating user accounts, and configuring your DNS records.

Export data from Zimbra: Next, you'll need to export your data from Zimbra. This can be done using the Zimbra Admin Console or by using a third-party tool.

Convert the exported data: Once you have exported your data from Zimbra, you may need to convert it to a format that is compatible with Office 365. This will depend on the type of data you are migrating.

Import data into Office 365: Finally, you can import the converted data into Office 365. This can be done using the Office 365 Admin Center or by using a third-party tool.

Verify data integrity: After importing the data, it's important to verify that it has been migrated correctly. This may involve spot-checking data and comparing it to the original source.

Greetings,
Peter