Goal:
    z : Z  z0 : Z  z1 : Z  z2 : Z  H : (z <= z0)%Z  H0 : (z1 <= z2)%Z
  ============================
   (z + z1 <= z0 + z2)%Z


DEBUG:Going to execute:
fun flags =>
             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