TeX source:
\begin{array}{rcl}\dfrac{z_1}{z_2} &=&\dfrac{3\left(\cos\left(\dfrac{\pi}{3}\right)+i\sin\left(\dfrac{\pi}{3}\right)\right)}{\frac{1}{4}\left(\cos\left(\dfrac{5\pi}{9}\right)+i\sin\left(\dfrac{5\pi}{9}\right)\right)} \\ \\ &=& \dfrac{3}{\frac{1}{4}}\left(\cos\left(\dfrac{\pi}{3}-\dfrac{5\pi}{9}\right)+i\sin\left(\dfrac{\pi}{3}-\dfrac{5\pi}{9}\right)\right) \\ \\ &=&12\left(\cos\left(\dfrac{-2\pi}{9}\right)+i\sin\left(\dfrac{-2\pi}{9}\right)\right) \\ \\ &=& 12\left(\cos\left(\dfrac{16\pi}{9}\right)+i\sin\left(\dfrac{16\pi}{9}\right)\right)\end{array}