I know that,
$S=\left(\displaystyle\frac{1}{1^3}+\frac{1}{5^3}+\frac{1}{9^3}\cdots\right) - \left(\displaystyle\frac{1}{3^3}+\frac{1}{7^3}+\frac{1}{11^3}\cdots\right)$
which is why it probably holds some kind of relation to the zeta-function. I tried looking it up on the internet but couldn't find anything related to $\zeta{(2k+1)}$
I want to show that $S=\displaystyle\frac{\pi^2}{32}$
Any hints ? (not asking for a complete solution) Thanks.