$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
5.13
\begin{equation} \begin{gathered}\label{equation:existence-uniqueness-cocartesian-lift} \xymatrix@R =50pt@C=50pt{ \{ 0\} \times K \ar [r]^-{H_0} \ar [d] & \operatorname{\mathcal{E}}\ar [d]^{U} \\ \Delta ^1 \times K \ar [r]^-{\overline{H}} \ar@ {-->}[ur]^{H} & \operatorname{\mathcal{C}}. } \end{gathered} \end{equation}