How many movies have John Mathot and Robert Hughes collaborated on?

They have worked on 2 movies together! Their first movie together was Phineas and Ferb: Star Wars (2014) while their highest rated movie together was Phineas and Ferb: The O.W.C.A. Files (2015). They have not worked together since Phineas and Ferb: The O.W.C.A. Files (2015).