To migrate from Zimbra to Gmail, you can follow these general steps:

Enable IMAP access in your Zimbra account: Log in to your Zimbra account and enable IMAP access. This will allow you to transfer your emails and other data from Zimbra to Gmail.

Create a Gmail account: If you don't already have a Gmail account, create one by visiting the Gmail website and following the instructions to sign up.

Configure Gmail account to allow IMAP access: Log in to your Gmail account and enable IMAP access by going to Settings > Forwarding and POP/IMAP.

Use IMAP to transfer data from Zimbra to Gmail: Using an email client such as Thunderbird or Outlook, configure your Zimbra account and your Gmail account to access each other via IMAP. Then, you can drag and drop or copy and paste your emails, contacts, and other data from Zimbra to Gmail.

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

Greetings,
Peter