Here's how to use your Apple TV Remote for Apple TV 4K or Apple TV (4th generation) to navigate through the Zattoo app:
Switching channels: Swipe left or right to switch channels or open the channel list by swiping up on Touch surface and then select Favorites / All channels / Categories.
Open channel list: In Live TV > Swipe up on Touch surface then select Favorites / All channels / Categories.
Pause/Resume: Play/Pause button on remote control or press to click on Touch surface.
Go forward/Go back: press to click on Touch surface, then swipe to right or left.
Subtitles: Swipe down > Subtitle > select
Change audio track: Swipe down > Audio > select
Restart/Replay: Swipe down > Info & controls > Replay
Go step back: Press Menu button to go back to the step before.
Recording options: Swipe Down > Info & controls > Recording Options
Open details from the player: Swipe down > Info & controls > Details
Volume: Press +/- button.
Open Menu: Press Menu button.
Close app: Press Apple TV App/Home button.
You can also use the Apple TV Remote app to navigate through the Zattoo app with touch gestures.