Inductive Forall2' (A B : Type) (R : A -> B -> Type) : list A -> list B -> Type :=
Forall2'_nil : Forall2' R [] []
| Forall2'_cons : forall (x : A) (y : B) (l : list A) (l' : list B),
R x y -> Forall2' R l l' -> Forall2' R (x :: l) (y :: l').

Lemma Forall2_trans_rel (A : Type) (R1 R2 : A -> A -> Prop) (l1 l2 : list A) : (forall x y, R1 x y -> R2 x y) -> Forall2 R1 l1 l2 -> Forall2 R2 l1 l2.