The other two solutions are only half right and since not everyone reads comments, I figured I'd post one as well.
Gino's setup for the 9 different difficulty matches is correct. However, he fails to tell you that you have to beat them all a second time while playing as whichever side you didn't win the first nine with. Thanks to yossariano for confirming this. I'm unsure why gino never updated his solution with this pertinent information.
So, you have 9 different matches to win with each side for a total of 18 matches. This doesn't have to be done in one sitting thank goodness. I used default settings and played the first map on all matches.