better traversal for more sharing in zo-marshal and some refactoring.
better traversal for more sharing in zo-marshal and some refactoring.

original commit: f4abd35f5c781b0ad8ce6c10dda33eac0f798836

mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket