$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
7.2
\begin{equation} \begin{gathered}\label{equation:U-colimit-by-morphism-space2} \xymatrix@R =50pt@C=50pt{ \{ C\} \times _{ \operatorname{\mathcal{C}}} \operatorname{\mathcal{C}}_{ / \overline{f} } \ar [r] \ar [d] & \{ C\} \times _{\operatorname{\mathcal{C}}} \operatorname{\mathcal{C}}_{/f} \ar [d] \\ \{ U(C) \} \times _{\operatorname{\mathcal{D}}} \operatorname{\mathcal{D}}_{ / (U \circ \overline{f} )} \ar [r] & \{ U(C) \} \times _{\operatorname{\mathcal{D}}} \operatorname{\mathcal{D}}_{ / (U \circ f) }. } \end{gathered} \end{equation}