intros a H'; red in |- *; intros H'0; absurd (zeroP a); auto.
apply zeroP_comp_eqTerm with (a := invTerm (invTerm a)); auto.
apply zeroP_invTerm_zeroP; auto.
apply eqTerm_sym; apply invTerm_invol; auto.
Qed.
Hint Resolve nZero_invTerm_nZero.
Set Implicit Arguments.
Unset Strict Implicit.
Definition T1 : Term.
exact (A1, M1).
Defined.
Set Strict Implicit.
Unset Implicit Arguments.

Theorem T1_nz : ~ zeroP T1.
simpl in |- *; auto.