Migrating accounts from a Shared Host to a VPS

Hi Guys hope some one can shed some light on the best practise for doing this. We have for some 5+ years had clients on a Cpanel accounts under our WHM account. The majority of these account exist for DNS only, maybe some 25% are hosted and email as well. The current host has become very unreliable over the last few months - effectively we lose DNS and it effects all other services. So I got the host to export my DNS Zone files and I imported them into a new WHM VPS account - where we now are root. Everything (DNS records) is essentially under the system account. I have set up two clusters in different locations so the DNS is now more robust and it is all working, and I have move a lot of the Name Server entries to use this set-up. However the current Hosting is still unreliable and I want to migrate all the accounts across. When moving one today I got the message "Account Creation Status: failed Sorry, a DNS entry for ABCDEF.COM already exists, please delete it first (from all servers in the DNS cluster)." This seems to tell me I would need to redirect the Name Servers back to the old host (check the DNS hasn't been modified in the mean time), delete the DNS entries here, Create the account, modify the DNS, change the Name Servers back. This seems very time consuming ( I have about 100 of these to do) and in some cases I do not have Registry access to the domain so asking the client to keep changing Name Server entries seems poor form. Is this the right approach?