16z²(4x-2y)²+12z²(y-2x)³
=16z²[2(2x-y)]²-12z²(2x-y)³
=64z²(2x-y)²-12z²(2x-y)³
=4z²(2x-y)²[16-3(2x-y)]
=4z²(2x-y)²(3y-6x+16)