Put some salt on the courgettes and let them in a colander to get the excess water out. Squeeze them also with your hands. Saute the onions with the drained courgettes in a pan by using the olive oil. After 2'-3' add salt, pepper and mint or dill. Stir and let them cool.
Add to the courgette-onions mixture the beaten eggs and all the cheeses. Stir well.
Grease a baking dish with the olive oil. Lay the pastry dough sheet in it by covering bottom and sides. Pour the filling mixture inside and bake the pie for 35'-40' in preheated oven to 200 ° C.