Talking about Zone 2… I’ve had good results (in my view) for sub Zone2 work (maffetone method) and I actually achieved good results (for my age group) in trail running. So I stuck w/ it (almost exclusively which was a mistake)
When came to my “A” race, I blew my quads cos they weren’t able to handle the NON Zone2 stresses I was throwing at it.
Power/Hr at Z2 is a good metric to be looking at as well I think. I also agree that there’s a lot of literature (science backed as well) and it’s hard to digest all of them and w/ the differing opinons (that are science backed as well).
Then there’s the “what works for you, doesn’t work for me” like for Sepp Kuss. (https://www.velonews.com/training/pros-cons-and-optimization-tips-for-indoor-riding/)