Find the mass of the cylinder $\displaystyle S:0<=z<=h$, $\displaystyle x^2+y^2<=a^2$ if the density at the point $\displaystyle (x,y,z)$ is $\displaystyle \delta = 10z^4+6(x^2-y^2)^2$.

I think we should use the cylincal polar method to do this, however i have problem converting this into the polar form, which is $\displaystyle x=rcos\theta$, $\displaystyle y =rsin\theta$,$\displaystyle z=z$