Preheat the oven to 425 degrees.
Cook gnocchi according to package directions (usually it isn't for more than 2-3 min).
Meanwhile, melt butter either in large saucepan or large cast iron pan. Use the cast iron if you have it because then it can go right into the oven from there.
Add garlic and saute for 30 seconds. Add drained gnocchi, cream, parmesan cheese, lemon zest, salt and pepper, tossing all together. Add all the veggies, then toss again.
If you're not using the cast iron pan, transfer mixture from large frying pan to a large casserole dish. Sprinkle basil overtop, then top with slices of mozzarella cheese and bake for 15 min.
Remove from oven and serve right away!