I’ve tried numerous times, even using ASIO4ALL which makes it ‘achievable’ but too unstable and kills performance. Outside of that, You are limited to one ASIO driver at a time.
What interfaces are you using? It’s possible you are using 2 from the same manufacturer and thus using a single driver, which is linking for you in the background. For example i have 2 Focusrite Saffires that run via firewire and they link together due to focusrites own linking ability - again, this is because it’s all going through a single driver.
As a real world example of what someone would like to do, i couldn’t use a Yamaha Montage’s audio interface with my primary firewire interface, other than within MacOS. This is due to being on seperate ASIO Drivers.
So please follow your own logic and read what i posted previously:-
With ASIO you cannot. You are limited to one driver at once. That’s literally what’s being discussed here.