Any external directory group is created in Zinc, by default it is placed into a folder named “External Directory Groups”, unless you select another default folder on the main Settings screen in the Zinc Admin Console.
Your external directory Zinc groups cannot be deleted in Zinc nor can you add users to or remove users from these groups or change their name in Zinc -- all of that must be done in your external directory.
If you delete a group in your external directory, the Zinc group will remain intact as a regular unlinked group with its current members and administrators. You can delete this group in Zinc once it becomes a regular, unlinked Official Group.
You can unlink an external directory Zinc Group from your external directory via the Zinc admin console, and the group will remain intact in Zinc as a regular Official Group that is no longer syncing with your external directory.