simp only [mem_sep_iff, interpret_memDom', interpret_inr, interpret_inl,
  and_iff_right_iff_imp, forall_exists_index]
V : Type u_1
inst✝ : Zermelo V
r x y z : V
⊢ x ∈ sep (BoundedFormula.memDom (Sum.inr 0) (Sum.inl ())) (fun x => r) (⋃ ⋃ r) ↔ ∃ z, opair x z ∈ r
V : Type u_1
inst✝ : Zermelo V
r x y z : V
⊢ ∀ (x_1 : V), opair x x_1 ∈ r → x ∈ ⋃ ⋃ r