$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
4.18
\begin{equation} \begin{gathered}\label{equation:isomorphism-extension} \xymatrix@R =50pt@C=50pt{ (A \times \Delta ^ n) \coprod _{ (A \times \Lambda ^{n}_{0} ) } (B \times \Lambda ^{n}_0) \ar [r]^-{F_0} \ar [d] & Y \ar [d]^{r} \\ B \times \Delta ^ n \ar [r]^-{ \overline{F} \circ \pi } \ar@ {-->}[ur]^{F} & S. } \end{gathered} \end{equation}