Zia is a village in the hills with a few bars, restaurants and souvenir shops but it's main feature is the amazing sunsets. You won't find any as beautiful anywhere else on the island.
The Greek night sometimes has the Zia trip included so that you can do in the same evening. It's a fantastic evening with lots of delicious food, wine and dancing. I would suggest not having lunch as there is a lot of food that seems to just keep coming.