$$(x^{2}-y^{2})(y^{2}+z^{2})$$
$-y^{4}+\left(xy\right)^{2}+\left(xz\right)^{2}-\left(yz\right)^{2}$
$\left(x^{2}-y^{2}\right)\left(y^{2}+z^{2}\right)$
