2x＾3－4x＾2y－x＾2z＋2xy＾2＋2xyz－y＾2z
=(2x^3-4x^2y+2xy^2)-(x^2z-2xyz+y^2z)
=2x(x^2-2xy+y^2)-z(x^2-2xy+y^2)
=2x(x-y)^2-z(x-y)^2
=(x-y)^2(2x-z)