Controller will transfer/allow the creation of the first zone that it will see. If it sees a “nixpal.com” on Server1 that doesn’t exists anywhere, it will transfer it to the slaves and will report “zone nixpal.com { … masters {server A}; }; .
If it sees -for example- a second “nixpal.com” zone in Server2 it will ignore it and notify controller.
Of course you can exclude a zone for testing or rapid transferring from a server A, to server B.
If you exclude “nixpal.com” from server “A”, it will change the master to server “B” in the Nodes.
Exclude is useful for transfers between servers, you can exclude multiple domains, and then transfer them.