Well... 350,-$ sounds a bit expensive!
I live in Germany and you can get a trip FRA-NYC rt for that price...
So, i can have a closer look at our travel agents/consolidators.
But i must say i know the market quite well and ZAG will not be extremely cheap because there´s not too much competition and the passengervolume is too small for consolidators. So i don´t know if this destination is on their list.
Of course i know some other "tricks"...

If you want me to check that for you i suggest you contact me direct with a PM
If your traveldate is march 2004 there´s still some time left for research.
It all depends whether you´re insisting on flying non-stop or not! There may be lower fares if you agree to travel e.g. FRA-PRG-ZAG (on CSA) vv. or FRA-LJU-ZAG (on Adria Aw.) vv. and so on.
I´ll start any research only if you ask me for that! I may have access to fares that are (intended) not for sale outside Germany...
Important for me would be on which exact dates you want to travel and how flexible (like a few days earlier or later) you could possibly be. It´s not a big problem if you´re not flexible but could result in a higher fare.

So, just let me know! (no, i don´t work in a travel agency nor with an airline)