One of the more interesting parts of this is how over time they developed different "mini drivers" as they call them.`In this part you will read that as we got to Vista they had better mini drivers that handle the streaming directly etc. 

What I read also is that the universal drivers should work for most audio devices but with limitations on accessing hardware features. 
This would explain FBB situation with the ZED under WDM. 

I like to use ASIO because I can swap sample rates without re launching SONAR.

Saves time and works real good.

Paul WASAPI is not an actual audio driver but replaced the KS mixer in Vista and beond. 

Thanks Cactus,this will require further study...

X2 on my Dell laptop with onboard "IDT High Definition audio" lists only WaveRT as input and output devices.

I'm not sure what happened, buy I could swear they were WASAPI when I had X1 installed.
I remember because it was the first time I ever saw mention of WASAPI.