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
∀ x0 x1 : ι → ο . wceq (cdc x0 x1) (co (co (co c9 c1 caddc) x0 cmul) x1 caddc).
The subproof is completed by applying H16.