How many movies have Kappei Yamaguchi and Shiro Hamaguchi collaborated on?

They have worked on 6 movies together! Their first movie together was One Piece: Dead End Adventure (2003) while their highest rated movie together was One Piece: Strong World (2009). They have not worked together since One Piece "3D2Y": Overcome Ace's Death! Luffy's Vow to his Friends (2014). They are most known for their adventure films together.