I think I may have the anwser for that.
In ZF, the routes are matched in reverse-order. So the last defined route, is the first matched.
In this case, you should define your /:person/:personname
route, then define the others static routes like about page, contact page, etc.
If I understand Zend correctly, it should work. This do that in clear:
url=/about
match route "/about"
url=/david/parker
match route "/:person/:personname"
not "/about" or "/contact"