Goal:
  
  A : Type
  B : Type
  R : nat → A → B → Type
  n : nat
  x : A
  y : B
  l : list A
  r : list B
  r0 : R n x y
  h : All2i R (S n) l r
  IHh : All2i (λ (i : nat) (x : A) (y : B), R (S n + #|l| - S i) x y) 0
          (List.rev l) (List.rev r)
  i : nat
  x0 : A
  y0 : B
  X : R (n + #|l| - i) x0 y0
  ============================
   (n + #|l| - i = n + S #|l| - S i)


DEBUG:Going to execute:
intros; Zify.zify_pre_hook; zify_elim_let; zify_op;
            Zify.zify_iter_specs; Zify.zify_to_euclidean_division_equations;
            Zify.zify_post_hook; zify_saturate