(** Multiply all elements except first occurance of x *)
Definition zmultDrop (x : Z) (l : Zlist) := zproduct (zdrop x l).

Lemma multdropzmultdrop :
forall (q : nat) (qlist : natlist),
Z_of_nat (multDrop q qlist) =
zmultDrop (Z_of_nat q) (map nat Z Z_of_nat qlist).