\[\left( 2x^{3}y - 3y \right)^{2} =\]
\[= 4x^{6}y^{2} - 12x^{3}y \cdot y + 9y^{2} =\]
\[= 4x^{6}y^{2} - 12x^{3}y^{2} + 9y^{2}.\]