A regular and very knowledgeable Hometalker named Kevin wrote this article that should help you:
Thanks for the kind words Steve...In addition to the copper and zinc treatments Heavy shade can contribute to more ideal conditions for moss growth. Some folks will prune back trees that may shade a roof, this helps too.
Thank you very, very much, Steve from Colorado. The weather is finally starting to get nice and I will fight the "Moss". Have a nice evening. And I always thought that zinc was the "magic" metal - it is copper.