I chose a female Zon, as I were told they are not so aggressive around sexual maturity! but I have only the breeders say so that she is a female! I am going to get her DNA tested as I swear she is a Male LOL
I am told that there is only a slight difference between the 2 Sexes, but I also think it depends on the individual Bird.
No kidding, Wendy! I am horrible at "guessing" sexes, but I just looked at the pictures you posted of Codie, and I "think" she's a girl. How does she perch? Are her feet always pretty close together, or does she spread them apart a bit?
From my understanding with Amazons, the males tend to be more aggressive during breeding season than the females. Of course I currently only have one sexually mature Amazon (Hunter), and she's NEVER had a mean bone in her body.

I am very lucky!
When I still had Quincy, a male DYH, he "could" be a little stand-off-ish at times, but never downright aggressive.