I've resumed the Zimbra Live sync page and made scripts out of it, which are now live on GitLab.com open for collaboration!
From the wiki page:
This is an experimental solution to providing near-live synchronisation between two Zimbra servers so that one of them is live and the other is kept in a warm or very warm standby state.
The system is symmetrical. The sync can work in reverse when the mirror server becomes the active server. This allows easy fall-back to the original server once the failover condition is resolved.
Feedback and contributions are welcome.