Zahark music is http://www.youtube.com/watch?v=rBWrC8hwy40 arranged.
Cobols music seems http://www.youtube.com/watch?v=rBWrC8hwy40.

Seems that the most except first chocobo are arrangements to fit "well" in the game.

If someone has to take over the music composing must be Naoshi Mizuta.