Transparent Z.of_nat.

Lemma Forall2_upd_Znth_l : forall {A B}{d: Inhabitant B} (P : A -> B -> Prop) l1 l2 i x, Forall2 P l1 l2 ->
P x (Znth i l2) -> 0 <= i < Zlength l1 -> Forall2 P (upd_Znth i l1 x) l2.