Hmmm... I just noticed that this question about Zeon soldier cosplay was posted way back in 2004... I wonder if Aris-Sempai is still around...
Nevertheless, I'll post this for those who want to look at it:
There is some variation among the uniforms of the various Zeon soldiers, but if you want one with a short cape containing the bird-like insignia on the front... I've made one of those capes before for my Char Aznable costume.
I took a black shirt (with a high neck), cut it to the appropriate shape, then used red and yellow fabric paints to put on the non-black parts. My method was to take some posterboard and cut out some openings in the shape of the designs I wanted, and then use those as a stencil to paint on the various patterns.
As for the epaulets (shoulder ornaments), I just cut those out of some yellow cloth. I made sure I added some anti-fray glue (available at craft stores such as Michael's) to the thin parts... if I hadn't done that, they would have probably frayed and fallen off.
A frog in a well does not know the ocean.
It is a wise man who accepts the limits of his wisdom.