Or go to the chat tab option (right click on tab) and filter what you want/don't want to see in the window...
I did the filtering several times and after about half an hour my screen would flash and it would go back to normal and I had to keep filtering it. I HATE HATE HATE zone chat. Wish it would just let me see the people in my group and those on my friends list and that it, or turn it off completely. I am so sick of seeing spam.