smc

First, note that we can pull the exponents out of every factor, since they are all squared. This results in ${\left(\frac{(x+1)(x^2-x+1)}{x^3+1}\right)}^4\cdot {\left(\frac{(x-1)(x^2+x+1)}{x^3-1}\right)}^4$ Now, multiplying the numerators together gives ${\left(\frac{x^3+1}{x^3+1}\right)}^4\cdot {\left(\frac{x^3-1}{x^3-1}\right)}^4$, which simplifies to $\boxed{1}$.