In Zones, workout measurement can only be used with Apple Watch.
If you do not have an Apple Watch, you can not use Zones' functionality to its fullest, but you can use it by linking other applications and devices.
You can see the workout results measured by other app.
Zones app reads workouts via Apple Health (HealthKit).
Please use other apps with cooperation function to Apple Health.
Please also refer to Workouts registered by other app.