Wash all vegetables thoroughly. Trim the woody ends from your asparagus, then slice into 2-inch pieces. Halve the cherry tomatoes and mince the garlic. Create an ice bath for blanching your asparagus and peas if desired.
Bring a large pot of generously salted water to a rolling boil. Add the pasta and cook until al dente, usually 1-2 minutes less than package instructions suggest.
While the pasta cooks, blanch the asparagus and fresh peas in the same pot for the last 2 minutes of cooking time. If using frozen peas, add them in the final minute.
In a large skillet over medium heat, warm the olive oil and butter. Add minced garlic and sauté until fragrant but not browned, about 30 seconds. Add the red pepper flakes if using.
Using tongs, transfer the cooked pasta and blanched vegetables directly into the skillet, bringing along some of the starchy pasta water. Add the zucchini, cherry tomatoes, and spinach. Toss everything together and let cook for 1-2 minutes until the spinach wilts and tomatoes slightly soften.
Remove the skillet from heat. Add lemon zest, lemon juice, fresh herbs, and Parmesan cheese. Toss everything together, adding a splash of reserved pasta water if needed to create a light, silky sauce that coats every strand. Season with salt and pepper to taste.