Preheat oven to 180°C / 350°F.
Lightly grease a baking dish with olive oil.
Slice zucchini into thin rounds.
Crack eggs into a bowl, add salt and black pepper, and whisk until smooth.
Stir fresh spinach into the beaten eggs.
Arrange a layer of zucchini slices on the bottom of the dish.
Pour the egg and spinach mixture over the zucchini.
Sprinkle grated cheese on top.
Add another layer of zucchini slices and finish with a little more cheese.
Bake for 20–25 minutes until set and golden on top.