How can I prove the equality between the following summations and products?
$$\frac{\sum_{m=0}^{M}{b_m z^{-m}}} {\sum_{n=0}^{N}{a_n z^{-n}}}= \frac{b_0}{a_0} \frac{\prod_{m=0}^{M}{1-c_m z^{-1}}}{\prod_{n=0}^{N}{1-d_n z^{-1}}}$$
Thank you for your help.