(* The property of a  number to divide another one 
     (Ndivides n m) shoud be read as m divides n *)
 
Definition Zdivides (n m : Z) := exists q : Z, n = (m * q)%Z.

Theorem ZdividesZquotientInv : forall n m : Z, n = (Zquotient n m * m)%Z -> Zdivides n m.