I've been working on removing the soon to be decommissioned Zoom Mac Outlook Plugin and implementing the new Zoom Outlook Add-In from the Microsoft store. I've found a way to remove the plugin here.
My office 365 admin has enabled the zoom plugin already and I can see it from Outlook for Web as enabled.
The issue is that across all my machines running either office 2016 or 2019 the add-in options are completely missing.
Are you using a Volume License for Office 2016/19?
If so, you will need to remove the volume license and use an o365 license for the new add-ins to be available.