Deleting primary Zimbra admin mailbox

How can we delete a primary Zimbra admin mailbox? The delete option is greyed out at the moment.

While logged into the Control Panel:

  1. Create a new user
  2. Set them as admin
  3. Log out of the Control Panel
  4. Log in to the Control Panel as new user
  5. Delete old user

You cannot delete a user you are logged in as.