unfold Zle in |- *; red in |- *; intros H'2; discriminate.
Qed.
Hint Resolve Zle_abs: zarith.

Theorem ZleAbs :
forall (z : Z) (n : nat),
(- Z_of_nat n <= z)%Z -> (z <= Z_of_nat n)%Z -> Zabs_nat z <= n.