First, you need to thaw the puff pastry overnight in the fridge.
Clean the onion and cut it in half, lengthwise, then slice it.
Clean the zucchini and cut them in half, lengthwise, then slice them.
Put the oil in the pan, add the onion and cook for 3 minutes then add the zucchini, a pinch of salt, pepper and cook, on medium flame for about 10-15 minutes, or until the zucchini have softened.
Let the zucchini cool completely.
Cut the mozzarella in cubes.
Grate the goat cheese.
Cut a piece of parchment paper for the baking pan, add the puff pastry and with a fork prick the dough.
In a bowl, brake the eggs, add the cold zucchini, the cheeses and mix well.
Pre-heat the oven at 355F.
Pour the mixture in the baking pan, level with a fork and put it in the oven for 30-40 minutes, or until it forms a golden crust