Sorry, a DNS entry for xxxxx.com already exists

Go to WHM > DNS Functions > Edit DNS Zone, and search for the xxxxx.com. If the DNS zone file exists there then you need to first check that how that domain is configured on your server.You can check that by looking into httpd.conf file. If it is not configured then you can simply delete the DNS zone file from WHM > DNS Functions > Delete DNS Zone.

If DNS zone file doesn't appear in WHM > DNS Functions > Edit DNS Zone, then login to your server via SSH and look for the entry of domain in /etc/named.conf file and if exists remove the entry.

 

If its a new server then you probably have not setup the server correctly.

 

Remove references from these files. You should have no trouble
creating the account afterward. I find this happens with domain name changes
on the account in question.

/usr/local/apache/conf/httpd.conf
/var/cpanel/users
/var/named
/etc/localdomains
/etc/named.conf
/etc/passwd
/etc/shadow
/etc/trueuserdomains
/etc/trueuserowners
/etc/userdomains
/etc/vdomainaliases
/etc/valiases
/etc/vfilters
/etc/vftp
/etc/vmail