You do not need to re-zone for the changed WWN for the alias.  All that needs to be done is to re-activate the zone once the changes have been made.
I am working on the brocade switch and just wanted to know a simple thing...i have in past used WWN and not alias against them in zones...now if i add a new wwn to an alias ..do I have to go and rezone them again...I mean when i have WWN , then i need to delete the old WWN and change it with new WWN and activate the zones again , would that be the case in Brocade as well using Alias in zoning .. 
Add WWN to Alias - need zone activation