The value of $\frac{(x−y)^3 +(y−z)^3 +(z−x)^3}{(x^2 −y^2)^3 +(y^2 −z^2)+(z^2 −x^2)^3}$ where $x ≠ y ≠ z$, is:

0 $\frac{1}{(x+y+z)}$ $\frac{1}{(x+y)(y+z)(z+x)}$ 1

$\frac{1}{(x+y)(y+z)(z+x)}$