Define a domains addresses sole in terms of another

[John Steel]

Say I have this definition:

$TTL    86400

@       IN      SOA     ns.example1.com. system.admin.example1.com. (
                        1132657947      ; Serial
                        10800   ; Refresh
                        3600    ; Retry
                        604800  ; Expire
                        86400 ) ; Minimum

example1.com.             IN NS      ns.example1.com.
example1.com.             IN NS      ns0.example1.com.
example1.com.             IN NS      ns0.example1.net.

ns.example1.com.          IN A       1.2.3.4
example1.com.             IN A       1.2.3.4

www                              IN CNAME   example1.com.
webmail                          IN CNAME   www
ftp                              IN CNAME   www
mail                             IN CNAME   www

example1.com.             IN MX  10  mail.example1.com.

As there are many other parked domains, plus TLD variations of example1.com,
it would be useful to define their recs soley in terms of the above. In 
other words,
where 1.2.3.4 appears in these slave domains I really want something 
like example1.com,
and no IP addresses. The point is during server moves etc I would only 
need to update the
1 record, rather than all the individual ones as at present. Is this 
possible please?

Thanks.

-- John
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