Kerodon

\begin{equation} \begin{gathered}\label{equation:all-squares-in-QCat3} \xymatrix@R =50pt@C=50pt{ \operatorname{\mathcal{C}}'_{0} \times _{\operatorname{\mathcal{C}}} \operatorname{\mathcal{C}}_{1} \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}