The Heart Rate Zones are fixed and they are not editable.

The Heart rate zones are calculated based on your maximum heart rate.

Peak performance
90 -100% Improves your short high intensity performance
Anaerobic intensive
80 - 90% Develops your anaerobic high intensity performance
Aerobic fitness
70 - 80% Enhances aerobic fitness and cardiovascular performance
Fat burn and endurance
60 - 70% Develops aerobic endurance and increases fat metabolism
Warmup and Recovery
50–60% Gets your body ready for exercise and accelerates your recovery

iPhone app only!
You can enable Voice feedback to notify you when you are crossing HR zone lines.