$$3x^{4}(y^{2}-4)+2x^{2}(y^{2}-4)-6(y^{2}-4)$$
$\left(y^{2}-4\right)\left(3x^{4}+2x^{2}-6\right)$
$24+2\left(xy\right)^{2}-6y^{2}+3y^{2}x^{4}-8x^{2}-12x^{4}$
