$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
7.3
\begin{equation} \begin{gathered}\label{equation:base-change-relative-limit5} \xymatrix@R =50pt@C=50pt{ \operatorname{\mathcal{C}}' \ar [rr]^{F'} \ar [dr]_{U'} \ar [dd]^{G} & & \operatorname{\mathcal{D}}' \ar [dl] \ar [dd] \\ & \operatorname{\mathcal{E}}' \ar [dd] & \\ \operatorname{\mathcal{C}}\ar [dr]_{ U } \ar [rr]^(.4){F} & & \operatorname{\mathcal{D}}\ar [dl]^{V} \\ & \operatorname{\mathcal{E}}& } \end{gathered} \end{equation}