Prove that the $g$ parameters can be obtained from the
$z$ parameters as
\[
\begin{aligned}
\mathbf{g}_{11}=& \frac{1}{\mathbf{z}_{11}}, & \mathbf{g}_{12}=-\frac{\mathbf{z}_{12}}{\mathbf{z}_{11}} \\
\mathbf{g}_{21} &=\frac{\mathbf{z}_{21}}{\mathbf{z}_{11}}, & \mathbf{g}_{22}=\frac{\Delta_{z}}{\mathbf{z}_{11}}
\end{aligned}
\]