Hi,
On going issues with this add on.
If a domain is moved between clients the DNS management at the client level doesn't update, and the previous user can still edit the DNS for the domain name.
In the Zones List it seems impossible to delete the domain, if you delete the zone the domain stays in the list, but the client it is assigned against is incorrect. Also a domain I had in WHMCS and added via Zone Import appears in the zone list, and subsequently the client that zone is assigned to. However I deleted the domain and the DNS, so its a dead link which is impossible to remove it seems.