Goal:
  
  G1 : t
  G2 : t
  l : labelling
  Gl := relabel_on G1 G2 l : t
  H : invariants G1
  preserves_edges : forall e : EdgeSet.elt,
                    EdgeSet.In e (E G1) -> EdgeSet.In e (E G2)
  HGl : correct_labelling G1 l
  H0 : invariants G2
  H1 : acyclic_no_loop G2
  embed : forall v1 v2 : VSet.elt,
          VSet.In v1 (V G1) ->
          VSet.In v2 (V G1) -> (lsp G2 v1 v2 <= lsp G1 v1 v2)%nbar
  x : V.t
  y : V.t
  w : Z
  n : Z
  Elsp : lsp G1 x y = Some n
  h : Z.of_nat (l x) + n <= Z.of_nat (l y)
  H2 : w <= n
  cstr : 0 <= Z.of_nat (l y)
  cstr0 : 0 <= Z.of_nat (l x)
  ============================
   (w <= Z.of_nat (l y) - Z.of_nat (l x))


DEBUG:Going to execute:
lazymatch Zify.zify_convert_to_euclidean_division_equations_flag
           with
           | true =>
               Zify.zify_internal_to_euclidean_division_equations
           | false => idtac
           end