It does seem like your hr and power zones are off from each other. I don't normally prescribe a "test", but i regularly (every couple weeks) prescribe baseline type workouts where I can Guage any drift or skew from previous efforts.
I prefer a 1x40' test to the 2x20' as I still find that people can overblow 2x20 more readily than a single straight 40'. I also tell people to ride it think you have to hold it for 60'. So, mentally 30' is only halfway.
Max HR is useless. Scale your zones using a threshold method of your choosing. Coggan / friel / etc.
Once you are reasonably fit, and your HR zones are established they don't move much with increases in fitness (heat load and fatigue... Yes). So, broadly speaking your z2hr will remain pretty static.
I prefer a 1x40' test to the 2x20' as I still find that people can overblow 2x20 more readily than a single straight 40'. I also tell people to ride it think you have to hold it for 60'. So, mentally 30' is only halfway.
Max HR is useless. Scale your zones using a threshold method of your choosing. Coggan / friel / etc.
Once you are reasonably fit, and your HR zones are established they don't move much with increases in fitness (heat load and fatigue... Yes). So, broadly speaking your z2hr will remain pretty static.