In a medium bowl, mix 1 1/2 cups crushed Caesar-style croutons with half the parmesan, 1 teaspoon grated lemon zest, and 1 tablespoon olive oil.
Season with salt and black pepper, then set aside.
Cook 1 pound of spaghetti or other long pasta in well-salted boiling water according to package instructions for al dente.
Reserve 1 1/2 cups of the cooking water, then drain the pasta.
Meanwhile, heat 3 tablespoons olive oil in a large skillet over medium-high heat.
Add 3 large zucchini (sliced into 1/4-inch rounds), 2 medium shallots (thinly sliced), and 1/4 teaspoon salt.
Cook, stirring often, until zucchini is softened and browned, about 20 to 25 minutes.
Stir in 3 minced garlic cloves and 1/4 teaspoon crushed red pepper, cooking until fragrant, about 1 to 2 minutes.
Add 2 tablespoons pasta water, scraping up any browned bits from the skillet.
Return pasta to the pot over medium heat.
Add 1 cup pasta water and 2 ounces cream cheese, stirring until the cream cheese melts and coats the pasta.
Mix in the caramelized vegetables and the remaining parmesan.
Toss to combine and coat the pasta with the sauce.
Remove from heat and stir in 1 tablespoon fresh lemon juice.
Season with salt, black pepper, and additional crushed red pepper to taste.
Add most of the fresh basil leaves, reserving some for garnish.
If needed, add more pasta water to reach desired consistency.
Serve topped with crouton breadcrumbs and reserved basil leaves.