Let \(z=a+bi\). \(|z| = \sqrt{a^2+b^2}\), so:
\(|z_a| = \sqrt{0+15^2} = 15
eq \sqrt{17} \\ |z_b| = \sqrt{0+17^2} = 17
eq \sqrt{17} \\ |z_c| = \sqrt{20^2+3^2} \ \textgreater \ \sqrt{20^2} = 20\ \textgreater \ \sqrt{17} \\\\ \boxed{|z_d| = \sqrt{4^2+1^2} = \sqrt{16+1} = \sqrt{17}}\)
