Definition Branch_of_Branch_to_Branch_inv {T : preZFS} (x : T) (y : Branch T x) : pr1 (Upw_to_TRRGraph (pr1 T) (pr1 y)) → pr1 (Upw_to_TRRGraph (preZFS_Branch T x) y) := λ X, ((pr1 X ,, pr12 (pr222 (pr11 T)) x (pr1 y) (pr1 X) (pr2 y) (pr2 X)) ,, pr2 X).