Definition zero_opp (C:category) : ZeroObject C -> ZeroObject C^op. Proof. intro z. induction z as [z k]. exists z. induction (opp_opp_precat C). exact (pr2 k,,pr1 k). Defined.
Require Import UniMath.Foundations.Preamble. Require Import UniMath.CategoryTheory.Core.Categories. Require Import UniMath.CategoryTheory.Core.Isos. Require Import UniMath.CategoryTheory.Core.Functors. Require Import UniMath.CategoryTheory.Core.Univalence. Require Import Require Import Require Import UniMath.MoreFoundations.Tactics.