Module Type ZMulOrderProp (Import Z : ZAxiomsMiniSig').
Include ZAddOrderProp Z.
Notation mul_pos := lt_0_mul (only parsing).
Notation mul_neg := lt_mul_0 (only parsing).

Theorem le_0_mul :
forall n m, 0 <= n * m -> 0 <= n /\ 0 <= m \/ n <= 0 /\ m <= 0.