The ezpolar command has a return argument. This is a handle to the graphics object it creates. You can set properties on that:
h = ezpolar('sin(2*t).*cos(3*t)',[0 pi])
h.LineStyle = ':'
h.Color = 'green'
h.LineWidth = 8
Note that the "dot notation" syntax was introduced in 2014b. The following version would work in earlier releases too.
h = ezpolar('sin(2*t).*cos(3*t)',[0 pi])
set(h,'LineStyle', ':', 'Color', 'green', 'LineWidth', 8)
