intros a1 H' b2 H'0 H'1;
apply (eqA_trans _ _ _ _ _ _ _ _ _ cs) with (y := multA A0 a1);
auto.
Qed.

Theorem zeroP_multTerm_r : forall a b : Term, zeroP a -> zeroP (multTerm b a).
intros a b; case a; case b; simpl in |- *; auto.