Choose a good sized wide pan with a tight-fitting lid. Heat the oil over medium heat, add the onion, garlic and half the herbs and cook, stirring occasionally, until softened, about 4 minutes.

Add the zucchini, stir about to coat with the oil, and season with pepper and 1/2 teaspoon salt. Lay the chard over the squash and season it with a few pinches of salt. Add the water, cover the pan, and lower the heat.

Cook gently until the zucchini is tender, 20 to 30 minutes. Remove the lid, stir the chard into the squash - gently so you don't smash it - and add the remaining herbs. Re-cover and cook for another few minutes. Taste for salt and pepper, drizzle with oil and serve. Accompany with lemon wedges.