Yes, zucchini is safe to feed your dog so long as it is properly prepared.
In fact, zucchini is one of the best foods you can add to your dog’s diet so long as you give them clean zucchini that does not have an oils, seasonings, or other ingredients. Zucchini prepared for dogs needs to be raw, steamed, or cooked, but not with oil or butter. (Cutting the zucchini into 1-inch chunks and microwaving them for 30 seconds at a time is quick and easy.)
Clean zucchini is OK for your dog, but zucchini bread is not. The added ingredients that make the bread taste so good are not healthy for dogs. Just set aside a cup of zucchini in its raw form while cooking your bread and share that with your dog later.