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