In a bowl, whisk the eggs, mozzarella cheese, salt and pepper and set aside.
Heat the olive oil in a frying pan over medium heat and add the zucchini. Heat for 3 minutes to soften, then add the cherry tomatoes for 1 minute. Remove the zucchini and tomatoes from the pan and set aside.
Next, add the spring onion and saute for 3-4 minutes to golden.
Once golden and aromatic, add the egg mixture to the pan and cook for a 3-5 minutes, until the egg starts to set.
Add the zucchini and cherry tomatoes to one half of the omelette and fold in half. Cook for another couple of minutes until cooked through.
Remove from the heat and serve with avocado.