Preheat your oven to 400°F (200°C) and generously grease a 12-cup muffin tin with olive oil or nonstick spray.

Using a box grater, shred the 2 medium zucchini and 2 medium potatoes. Place the shredded vegetables onto a clean kitchen towel and squeeze out as much liquid as possible.

In a large bowl, combine the dried, shredded zucchini and potatoes with the finely grated onion (if using), 2 large eggs, 1/2 cup grated Parmesan cheese, 1/2 cup breadcrumbs, 2 minced garlic cloves, 1 teaspoon salt, 1/2 teaspoon black pepper, and 1/2 teaspoon dried oregano. Mix thoroughly until all ingredients are well incorporated.

Spoon the mixture evenly into the prepared muffin cups, pressing down firmly with the back of a spoon to pack each cup tightly. This helps the muffins hold their shape and creates that crispy exterior.

Drizzle the 2 tablespoons of olive oil evenly over the tops of the muffins. Place the muffin tin in the preheated oven and bake for approximately 25-30 minutes, or until the tops are deeply golden and the edges appear crispy. Start checking around 20 minutes if your oven runs hot.

Remove the muffins from the oven and allow them to cool slightly in the tin. Once cooled enough, gently remove them using a knife or small spatula. Serve warm and enjoy their perfectly crispy texture and tender interior.