Goal:
    z : Z  z0 : Z  z1 : Z  H : (z <= z0)%Z
  ============================
   (z1 + z <= z1 + z0)%Z


DEBUG:Going to execute:
match reverse goal with
           | |- ?X1 => <Coq.Init.Tauto.is_unit_or_eq> flags X1; constructor 1
           | H:?X1 |- _ => <Coq.Init.Tauto.is_empty> flags X1; elim H
           | _ => Ltac.assumption
           end