After updating Zones: sums of time in Zones incorrect

After updating the Zones (and also running the zone update through all past activities), when plotting time in Zones in the Fitness tab, the single new Zones are shown correctly, but e.g. Z1+Z2 or Z3+Z4 gives quite random values.

The default combinations Z1+Z2 etc, always use the default Zone system.
For Custom zones, you need to apply the additions yourself.

Ok Thanks. Which of the 4 default zones models is used? And is there any way I can create the additions for my zones?

The built-in combinations for Heartrate zones

And for Power zones

You can define which one has priority on the Settings page per sports category. But that’s for the Totals page. In your Fitness chart you choose which ones you plot.

When you define Custom Zones, they appear in the list of plottable metrics as CZ…
To make combinations of those, I think you need to create Custom activity fields where a script adds them to your liking. The name of that Custom activity field will then also appear as a metric in the list.