Waited

Calculate the value of the follow expression:

$\large \frac{[(x+ y + z)^3 - x^3 - y^3 - z^3][(x + y + z)^3 - (x + y - z)^3 - (y + z - x)^3 - (z + x - y)^3]}{(xy + zx)(yz + xy)(zx + yz)}$

Notation:

$\large \left\{ \begin{aligned} xy + zx &\ne 0\\ yz + xy &\ne 0\\ zx + yz &\ne 0 \end{aligned} \right.$

This is part of the series: " It's easy, believe me! "