$$\frac{a+c}{a^{2}+ac+c^{2}}+\frac{a-c}{a^{2}-ac+c^{2}}+\frac{2c^{3}}{a^{4}+a^{2}c^{2}+c^{4}}$$
$\frac{2\left(a+c\right)}{a^{2}+ac+c^{2}}$
