Bind 9 ext and int zone

[Nick Allum]

Would anyone have any suggestions as to what options I might handle the
following situation.
We have a zone testthis.com which is and external zone on some external
NS servers. However they are also requesting that we host this zone
internally on our internal NS server to point to some development
servers with internal addressing.

I do not want to have to maintain any changes interally that are made
externally, so I am looking for an alternate solution.

Any suggestions would be much appreciated.

Nick