Here are some quick search results:
- Z2 training, optimal time, power vs HR
- Zone 2 Power vs Zone 2 HR (Should I increase power to move HR to Z2?)
- Z2 power vs Z2 HR
- Pacing endurance rides by power or HR? Benefits of short endurance rides
- How important is HR vs power for aerobic base training?
- Is there still a use case for Heart Rate? (HR)