Definition zle: forall (x y: Z), {x <= y} + {x > y} := Z_le_gt_dec.

(* Specifications: *)
Lemma zle_true:
forall (A: Type) (x y: Z) (a b: A),
x <= y -> (if zle x y then a else b) = a.
Lemma zle_false:
forall (A: Type) (x y: Z) (a b: A),
x > y -> (if zle x y then a else b) = b.