5. Given $\frac{x+y-z}{z}=\frac{x-y+z}{y}=\frac{-x+y+z}{x}$, and $x y z \neq 0$. Find the value of the fraction $\frac{(x+y)(y+z)(z+x)}{x y z}$.

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(Answer: -1 or 8 )