\frac{\partial}{\partial \theta}\left( \text{PH}^3 \frac{\partial \text{P}}{\partial \theta} \right) + \frac{\partial}{\partial \text{z}}\left( \text{PH}³ \frac{\partial \text{P}}{\partial \text{z}} \right) = \Lambda \frac{\partial}{\partial \theta} \left( \text{PH} \right) + 2 \Lambda v \frac{\partial}{\partial \tau} \left( \text{PH} \right)