The framerate near the terminals was from high single digits to mid-high teens. This surprised me because my framerates are fine (mid to high 20's) for KLAX and KJFK v2.
I wouldn't call your fps at KLAX or KJFK V2 very good either. But since you use an airplane which is very fps heavy, that might be the case. However, is to be expected that KLAX and KJFK V2 performs better than Zurich.
Zurich was released in 2007 and back then, such fps hungry airplane didn't existed so, there was more headroom to run the scenery. Is still a scenery that uses a lot of old techniques and lots of FS8/9 code, because it was designed when lots of users were still using FS9. The recent updates have just updated the airport to current status (new terminal B), but haven't changed much in the underlying technology.
KLAX is a 100% FSX native scenery with no slow legacy code, and KJFK V2 is a total remake that also use 100% FSX native code (that's why is a paid update for previous JFK users), so they will perform much better in FSX, which also explains why KLAX doesn't run very well on FS9.
So, it's normal that Zurich won't run in FSX as fast as it did in FS9 and would be slower than our FSX-only products. It would probably require a complete remake, like the one we did with KJFK V2, to offer the same level of performances, even when used together with the more complex add-ons available now. I guess your fps is reasonably good with a default airplane.