=[(x-2y)(x+2y)]^2(x^2+4y^2)^2-[x^4-(2y)^4]^2
=(x^2-4y^2)^2(x^2+4y^2)^2-[x^4-(2y)^4]^2
=(x^4-16y^4)^2-[x^4-16y^4]^2
=0
[(x+2y)^2*(x-2y)^2]^2*(x^2+4y^2)^2-[x^4-(2y)^4]^2
=[(x+2y)(x-2y)]^2*(x^2+4y^2)^2-[x^4-(2y)^4]^2
=(x^2-4y^2)^2*(x^2+4y^2)^2-[x^4-(2y)^4]^2
=[(x^2-4y^2)(x^2+4y^2)]^2-[x^4-(2y)^4]^2
=(x^4-16y^4)^2-[x^4-(2y)^4]^2
=0