Canonical dvdz_oppPred d := OpprPred (dvdz_zmod_closed d).
Canonical dvdz_zmodPred d := ZmodPred (dvdz_zmod_closed d).

Lemma Gauss_dvdz m n p :
coprimez m n -> (m * n %| p)%Z = (m %| p)%Z && (n %| p)%Z.