$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
7.73
\begin{equation} \begin{gathered}\label{equation:homotopy-equalizer-diagram} \xymatrix@R =50pt@C=50pt{ \operatorname{\mathcal{E}}\ar [r]^-{G} \ar [d] & \operatorname{\mathcal{D}}\ar [d]^-{ (F_0, F_1) } \\ \operatorname{\mathcal{C}}\ar [r]^-{ (\operatorname{id}, \operatorname{id}) } & \operatorname{\mathcal{C}}\times \operatorname{\mathcal{C}}} \end{gathered} \end{equation}