Preheat your oven to 375°F (190°C).

Generously grease a 9x13-inch baking dish with butter.

In a large mixing bowl, combine thinly sliced zucchinis, roughly chopped fresh spinach, and minced garlic. Drizzle with olive oil and toss to combine.

In another bowl, whisk together the ricotta cheese, eggs, and crumbled feta. Stir in dried oregano, basil, salt, and pepper.

Layer half of the zucchini and spinach mixture into the bottom of the prepared baking dish, pressing down lightly.

Spread half of the cheese and egg mixture evenly over the first layer of vegetables.

Add the remaining zucchini and spinach mixture on top, pressing gently. Spread the rest of the cheese mixture over this layer.

In a small bowl, combine breadcrumbs with grated Parmesan cheese. Mix well, then sprinkle evenly over the top layer.

Bake the casserole in the preheated oven for 35-40 minutes until the top is golden brown.

Let the casserole cool for a few minutes, then slice and serve warm.