Answer
$$\frac{\left(n-4\right)\left(n+4\right)}{\left(n^2+4\right)\left(n^2-4\right)}$$
Work Step by Step
To multiply fractions, we multiply the numerators by each other to get the new numerator, and we multiply the denominators by each other to get the new denominator. Note, we are asked to leave the answer in factored form. Doing this, we find:
$$ \frac{n-4}{n^2+4}\cdot \frac{n+4}{n^2-4}\\ \frac{\left(n-4\right)\left(n+4\right)}{\left(n^2+4\right)\left(n^2-4\right)}$$