How to plot |z| in a pole-zero map of a discrete time system ?

Hi,

I am trying to plot a pole-zero map of a discrete time system. I have used pzmap(mysys) and zgrid(zeta,wn2) to create my plot, where zeta = 0.5038 and wn2 = 0.2906 and I get this plot (see "My_Plot). But I also want to plot | z | = exp(-zeta*wn*T) and make my graph look more like "Desired_Plot". Any help would be greatly appreciated.