Hmm I wonder if antimicrox would allow you to combine two inputs into one composite input, I don’t have experience with it so I can’t say for sure but it seems like the kind of utility that would.

https://github.com/AntiMicroX/antimicrox

What I would do in this situation is map the controls to keyboard, then use a Controller-to-Keyboard mapping program to map all the controller buttons to the keyboard buttons. So map both controllers D-Pads to W-A-S-D (or arrows, or whatever really) then set those keyboard controls to your movement controls in the emulator.

https://www.reddit.com/r/EmulationOnPC/comments/165tewk/mapping_multiple_controllers_to_the_same_input/