Grind the zucchini and potatoes.
In a bowl, add the ground zucchini, ground potatoes, flour, myzithra cheese, egg, ground graviera cheese, parsley, salt, pepper and a little olive oil.
Stir well, and break the myzithra cheese in small bits.
Melt the butter.
Smear a baking pan with butter and lay one by one 5 Filo Pastry sheets, also smearing them with butter. Add the stuffing and spread it evenly. Cover in the same way.
Mix the egg yolk with a little water and smear it well on the pie surface.
Add the sesame and carve the pie.
Bake at 190 °C, with extra heat on the top and bottom oven elements and air, on the bottom rack, until golden brown all over.