I mostly use olive oil in my baking. It is another significant ingredient that helps this glazed lemon zucchini bread turn out moist. I don’t advice extra virgin olive oil though as it tastes much stronger than the regular one. Other than olive oil, which is also a way of cooking light, I think coconut oil, sunflower oil or canola oil would work fine too. As for butter, yes you can use it too but your bread won't be that moist and fluffy with it although the taste will be good.