Grate the zucchini, salt lightly, and drain in a colander for 15–20 minutes.
Squeeze out excess moisture.
Sauté onion in a little olive oil until translucent. Let it cool slightly.**If you prefer, you can grate them and add raw. In a large bowl, combine grated zucchini, 3 eggs, feta (or myzithra cheese), and the chopped herbs.
Season with salt and pepper.
Add the onion and zucchini mixture and mix everything well.
Preheat oven to 180°C (fan/ventilated).
Brush a baking dish with olive oil. Layer two phyllo sheets, brushing each with olive oil or melted butter.
Add a portion of the fillingm unevenly.
Add another single sheet of phyllo, brush with oil.
Repeat layering: phyllo, filling, phyllo…
Finish with two top phyllo sheets, brushing each with oil.
Lightly score the top, then brush with the beaten egg (eggwash) for a golden finish.
Bake for 40-45 minutes, or until golden and crisp.
Let cool slightly before cutting and serving.