We, at zSpace, haven't had time to seriously dig into SRP yet. It certainly seems promising for a range of reasons, and should be possible to integrate with zSpace. As you've discovered, they're not working together out-of-the-box right now. Chances are, you'll have to customize zCore for this to work.
Unity stopped supporting quad-buffer stereo in their game view window around version 5.4. That's why we provide our own special preview window that does it's own thing.
If you're really going to dig into SRP, I'd start looking at ZCore.UpdateCamera() to get a sense of how we handle the stereo that is used in actual builds. Essentially, we use Unity's built-in stereo camera and apply our own frustum and view matrices that we compute from the incoming tracking data.
You're in uncharted territory, but if you're ambitious enough to tackle it, more power to you. We'd love to hear how it goes! :-D
Feel free to use us as a resource as you tackle it and we'll do our best to shed light on any zSpace specifics.