=8x3y + z3y + 8x3z -2xz3 - y3(z +2x)= y(8x3+z3) +2xz(4x2-z2) - y3(2x+z) = y(2x+z)(4x2 - 2xz + z2) +2xz(2x+z)(2x-z) - y3(2x+z)
=(2x+z)(4x2y -2xyz + z2y + 4x2z -2xz2 - y3) = (2x+z)( 4x2y+ 4x2z - 2xyx- 2xz2 +z2y - y3) = (2x+z)[ 4x2(y+z) -2xz(y+z) + y(z+y)(z-y)]
= (2x+z)(y+z)( 4x2- 2xz +yz- y2) = (2x+z)(y+z)(4x2 - y2 -2xz + yz) = (2x+z)(y+z)[(2x-y)(2x+y) - z(2x-y)]
= (2x+y)(y+z)(2x-y)(2x+y-z)