yes but in garmin connect/mobile how can i change zone percentages based on HRR? i can't find itYou can't, because the Karvonen approach is not implicitly supported in Garmin Connect Mobile as the app (or Garmin Connect itself) stands today. However, nothing stops you from using a calculator or spreadsheet to determine the HR zone thresholds in terms of Beats Per Minute, if you want to use the Karvonen approach.
and if i changhe this on the watch it will overwrite everytime i sync!That's not true. Based on results observed in my experimentation, the values on the watch are not overwritten upon syncing with Garmin Connect Mobile if you do not go to the HR Zones section in GCM; my hypothesis is that GCM will not flag that HR zones values are something to compare with and/or sync onto the watch, unless you visit that section (or page) of the app.
Just bought a Forerunner 55. 'Over 6 years later' and the same issue remains. All heart rate zones on app showing the max Z1 166bpm-167bpm and all other zones the same. I've tried all the things above and none of them work. For an organisation that promotes activity, that's pretty lazy.