RE: The B/W Questions and Answers Thread
Trainers with the pokemon you said can be found here:
Klang are located here: Victory Road (an Ace Trainer), P2 Lab (Scientist Dudley)
There are no trainers that own a Zweilous
Braviary, Cynthia has one, but you can't battle her in Winter.
Vullaby is like zweilous, however can be found in the wild on Pokemon Black.
Mandibuzz is like it's pre evo, but can be found in the wild on Pokemon black.
I've used serebii to find theses locations, hope it helped.