Cut the zucchini in half crossways, then into quarters to make finger-sized pieces. In a large skillet, warm the olive oil and onion over medium heat until onion is translucent, about 2-4 minutes. Add zucchini, garlic, lemon zest, half the mint, tarragon and water. Stir well to combine. Reduce heat to low and cover. Cook, stirring occasionally, until zucchini is very tender (about 20 minutes). There should be some liquid left in the pan. Remove the lid, add the lemon juice, turn the heat to high and wait for the liquid to start bubbling. Remove from heat and set aside. Add remaining mint and pine nuts. Season with salt and pepper to taste. Serves 4.