Octave pzmap: format poles and zeros
Try the following code,

num=[1 3];
den=[1 5 20 16 0];
sys=tf(num,den);
pzmap(sys) h=pzmap(sys)

hh = findobj(gca,'type','line');
for jj=2:length(hh)
set(hh(jj),'MarkerSize',12,'MarkerEdgeColor','red','LineWidth',5);
end


source

And the result is,