updating a zone from another dns

[david.tansley at acelondon.co.uk]

hello,
 I currently have a  DNS server ( bind 8.2.1 ), due to a merge with another
company we need to update each others zone file for internal use.

To do this do  I need to add a NS record of their name server, also add a
'allow-transfer'
( named.conf) on my zone containing their DNS IP address. But then I lost, what
else do I require to make sure my zone gets refereshed. I have thought about
manually using named-xfer, but I would prefer to use the normal method.
assume, my dns is ( 192.168.2.10  with the domain name of example_UK.com )
their dns is ( 192.168.8.5 with the domain of example_US.com )

regard,
David,