I have mainly relied on HR. My cycling HRpeak from ramp tests and VO2max tests is 182-183, and Seiler advises his Z1 (in the three-zone model) should have HR in the range of 60-75% HRmax. Practically speaking, I have just aimed to have my HR in the range of 115 to 125 bpm for most of the year, and let the wattage fall where it may.
Chad McNeese created a hand-dandy spreadsheet summarizing the Seiler zones and the Coggan zones. I relied on this for most of my Endurance rides in 2022. Thanks, Chad!!
The coach I am working with does a lot of HR-based training, but based off of Coggan zones, which use threshold HR instead of HRmax as a reference. Given that my threshold HR seems to be around 162 bpm, my coach has advised me to push up the average HR on Endurance rides into the range of 128-141 bpm. This is quite a bit higher than what I had been doing, so it has been an adjustment and I am skeptical that I can really handle 15-17 hrs a week in this HR range.
As a compromise, I have been pushing my Endurance HR up in “baby steps,” like trying to get an average of 126 bpm on a 3hr Endurance ride, instead of 118 bpm. Definitely it means pushing more watts, but at what recovery cost? There’s the rub. We shall see how it goes… a work in progress!