A DNS entry for “domainame.com” already exists. You must remove this DNS entry from all servers in the DNS cluster to proceed.

I got this error while trying to add a domain as an Addon on the primary cPanel account. The domain is already pointing into another servers which also using the same DNS cluster and that was actually creating the problem.
I have tried a lot and got one solution

Please do follow the steps below:

Step1 : First I made a backup of DNS zone of domain

cp -rp /var/named/domain.com.db /var/named/domain.com.db_back

Step2 : SSH to server (Where we need to add the domain as Addon).

Step3 : Execute the following cPanel script:

/scripts/killdns domain.com

That’s it! Then try to add the domain as Addon. It should be okay now
Now, verify this through command line:

cat /var/cpanel/userdata/$user_name/main

That’s it