\xymatrix{
	A \xypo \ar[r] \arcof[d]_{(\simeq)}^i & C \ar[d]^j \\
	B \ar[r] & P
}
\qquad
\xymatrix{
	P \xypb \ar[r] \ar[d]^q & X \arfib[d]_{(\simeq)}^p \\
	Z \ar[r] & Y
}