[Feature request] Shortcuts to switch to window in previous/next zone

[kermitfrog]

Is your feature request related to a problem? Please describe.
When working with more windows than zones on the same virtual desktop, I will (obviously) put 2 windows in the same zone.
I'm currently using KWin's "Switch to Window to the Left/Right" shortcuts to switch between those, but this has drawbacks:

1. assuming I got windows 1 & 2 in the left zone and 3 on the right and 1 is active. Then switching right will activate 2 first, then switch to 3 the next time. This will also hide 1 behind 2, which is usually not what I intended.
2. if I had e.g. a left upper and left lower zone, I would need additional shortcuts to navigate between the windows.

Describe the solution you'd like
I'd like 2 new shortcuts to switch focus to whatever window is in front of the previous/next zone.
Switching to other windows inside the current zone is no problem, as there already is a shortcut for this.