intros P z; case z; simpl in |- *; auto.
Qed.

(* Specifications: *)
Theorem Zpred_Zle_Zabs_intro :
forall z1 z2 : Z,
(- Zpred z2 <= z1)%Z -> (z1 <= Zpred z2)%Z -> (Zabs z1 < z2)%Z.