Cook spaghetti according to package directions. Drain and toss with sauce. Enhance the sauce with extra olive oil, salt, and pepper to taste.
Preheat oven to 400°F (200°C). Beat egg in a large bowl, add zucchini rounds, and toss to coat.
In the same bowl, add panko, Parmesan cheese, lemon zest, salt, pepper, Italian seasoning, and garlic powder. Toss to coat the zucchini generously.
Arrange coated zucchini on a baking sheet. Spoon any remaining breadcrumb mixture over the zucchini. Drizzle with olive oil and bake for 15-20 minutes until golden brown.
Remove from oven, sprinkle with your choice of cheese (optional), and bake or broil for another 5 minutes.
Serve spaghetti in bowls topped with the cheesy crispy zucchini, fresh basil, a drizzle of olive oil, and red pepper flakes if desired.