1. The optical port on a ZP90 is an output, not an input.
2. Any use of a ‘Line-In’ type connection through Sonos would incur at least 75ms of delay, potentially ruining picture lip-sync.

Thank you a lot for your answer ! And if I am using only the sonos system with the input analog audio port, will it work ? Or is there any better way to connect a sonos system to an apple TV, without going through a TV ?

Inputting analog audio would suffer the delay I mentioned in point 2 above. 

Sonos make home theatre products specifically for connecting to TVs, which reduce the delay sufficiently for it usually not to be an issue.

Ooh ok thank you, but if there is a delay with the cables, how are you supposed to connect them to a TV, (without necessarily talking about the ZP90, because I’ve understood it was unnecessary for video but to connect directly to some Sonos speakers) ?

Sonos products designed for TV use have digital inputs, with no delay. Products not designed for TV (eg your ZP-90) have analog inputs, and have the 75ms delay.

Ok ! Thanks ! So I believe that connecting Sonos Play:1to a tv is impossible unless I have a sonos playbar right ?

And another Play:1 as you can only bond them to a Playbar in pairs. (Or a Beam or Arc or Playbase). A Beam on its own is the cheapest TV solution from Sonos.

And this assumes your PJ has optical out, and many inexplicably do not.

Thank you very much for clarifying this point! And for the optical cable, I am thinking of buying an HDMI converter!

My suggestion excludes your amplifier and speakers entirely, so before spending any more money you might want to get your entire proposal confirmed here. You likely need an HDMI switch with optical output, not a converter.