Preheat the oven to 180°C (350°F/Gas 4).
In a bowl, whisk the eggs, parsley and chives. Season with salt and pepper to taste.
Heat 1 tablespoon of the oil in a 20 cm (8 inch) non-stick ovenproof frying pan over medium–high heat. Cook the zucchini until lightly golden on both sides. Drain on paper towel.
In the same pan over medium heat, add 1 tablespoon of the oil and sauté the garlic, rosemary and thyme until fragrant and the garlic is soft.
Add the silverbeet and cook for 1 minute or until the greens start to wilt.
Remove from the heat and transfer the mixture to a bowl.
Heat the remaining oil in the same frying pan over medium heat.
Add the egg mixture and cook, without stirring, until the outside begins to set. Use a spatula to start stirring the eggs, lifting up the set egg so the uncooked egg runs underneath. Continue to cook for a further 1 minute, then spoon the silverbeet mixture and the grilled zucchini over the eggs, pressing down gently and spooning some of the raw egg over the top so the vegetables are covered.
Sprinkle with salt and pepper then transfer the pan to the oven.
Cook the frittata for 10–15 minutes or until the egg is golden on top and just set.
Serve sprinkled with pecorino and with bacon on the side, if desired.