Apply df_sub__df_neg__df_div__df_nn__df_2__df_3__df_4__df_5__df_6__df_7__df_8__df_9__df_10OLD__df_n0__df_xnn0__df_z__df_dec__df_uz with
wceq cz (crab (λ x0 . w3o (wceq (cv x0) cc0) (wcel (cv x0) cn) (wcel (cneg (cv x0)) cn)) (λ x0 . cr)).
The subproof is completed by applying H15.