$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
7.9
\begin{equation} \begin{gathered}\label{equation:categorical-pushout-cofinal} \xymatrix@R =50pt@C=50pt{ X \ar [r]^-{f} \ar [d] & Z \ar [d] \\ X' \ar [r]^-{f'} & Z'. } \end{gathered} \end{equation}