Press the puff pastry sheet onto a tart pan.
Wash the zucchini and grate it, or cut it in a fine julienne on the mandoline. Put the zucchini over a strainer and sprinkle some salt over it. The salt will help to take out some moisture, so leave the grated zucchini on the strainer for a few minutes.
Finely dice the mozzarella and crumble the feta. Set 1/4 of the crumbled feta aside as that will be used on the top.
Crack the eggs in a bowl and add a sprinkle of salt and pepper. Remember that you have already salted the zucchini and the feta is quite salty itself, so it is not necessary to add more than a sprinkle to the eggs. Whisk for a couple of minutes by hand.
Squeeze away any excess water from the zucchini and add them to the eggs. Add the mozzarella and feta. Mince the mint leaves and add them to the bowl - you can as well finely cut the leaves directly over the bowl with a pair of herb scissors. Stir to combine.
Pour mixture over puff pastry crust. Sprinkle the remaining feta all over the top.
Bake in the preheated oven at 200°C for 35 minutes.