$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
7.66
\begin{equation} \begin{gathered}\label{equation:all-squares-in-QCat} \xymatrix@R =50pt@C=50pt{ \operatorname{\mathcal{C}}_{01} \ar [r] \ar [d] & \operatorname{\mathcal{C}}_{0} \ar [d]^-{ F_0 } \\ \operatorname{\mathcal{C}}_1 \ar [r]^-{ F_1 } & \operatorname{\mathcal{C}}} \end{gathered} \end{equation}