$${ \left(xyz+xy \right) }^{ 2 } -2 { x }^{ 2 } { y }^{ 2 }$$
$\left(\left(z+1\right)^{2}-2\right)\left(xy\right)^{2}$
$2z\left(xy\right)^{2}+\left(xyz\right)^{2}-\left(xy\right)^{2}$
