I have just got sonos play. Can I plug in my iPhone directly into the speaker.

Depends on which speaker you got. If it's a PLAY:5, then yes, there's a line in on that speaker. None of the other speakers have a line in, though. The CONNECT and CONNECT:AMP also have analog line ins.

However, you can, from inside of the Sonos app, play music "from this iPhone", and that doesn't require a wired connection, and works on any Sonos speaker.

It’s a play 1 I think

Then my second paragraph applies.

Ok so I have zin play platform on my iPhone how can I get that to work

I have no idea what a zin play platform is, so I don't think I can help you. The Sonos controller app has the ability to "see" music stored in the Apple Music app, and play that music by treating your phone as if it were an NAS, and grabbing the data. But it isn't a system where you can "play anything that comes out of the phone's speaker", like a blue tooth or Airplay speaker is. However, Sonos has stated that they're currently working on an implementation of Airplay 2, although that's the extent of the knowledge we have on that, other than it will be released in 2018. At that point, assuming that you have a speaker from Sonos that can accept an Airplay 2 connection, you'll be able to "play" anything that would come out of the speaker on your iPhone on the Sonos system. We think. As I say, we really don't have all the details yet.

I am almost sure that play 1 will not accept Airplay 2 in the future as well. It will take newer Sonos hardware models.

Yea, someone called me out on that, and I have backed off on that statement until Sonos actually makes a formal announcement. For me, it's not worth arguing over, and until the give us the real lowdown, I'm going to avoid causing any anger 🙂