If you dont transfer list them and offer them to other teams, they'll get more unhappy AND they'll start to dislike you. That's a huge problem if you cant sell them for some reason.
If you DO transfer list and then offer them out, they will still get unhappy probably. But in this case they wont dislike you and that's important if you have to keep them.
Anyway, I wont sell Owen tbh. Not in the game. You might not like him irl, but he's awesome in the game. If you do sell him, look for alteast 20M
imo. And Fred is better than Briand (who's great too tbh) so I'd look at Fred first. He'll probably win you the league by himself.
Forget Zapata for now. He'll cost you 20M+. Not worth it if you're in your first season and need to strengthen. Buy some good, solid players who dont cost as much. Get Felipe (Udinese), who's an EXCELLENT CB. And he'll cost you about 5M only. Get Ignashevich for free as well. Will give you good cover. Make a few solid signings like there and get Zapata next season when you have more cash.
As for Smith, no idea there mate. But I'd look to get atleast what he's valued at. I did read somewhere though that if you keep him for a season he can be sold for more. Not sure.