Transparent Z.of_nat.

Lemma Forall2_forall_Znth : forall {A B}{d1: Inhabitant A}{d2: Inhabitant B}  (P : A -> B -> Prop) l1 l2,
Forall2 P l1 l2 <->
Zlength l1 = Zlength l2 /\ (forall i, 0 <= i < Zlength l1 -> P (Znth i l1) (Znth i l2)).