Combine the broth, fettuccine, onion, zucchini, yellow squash, mushrooms, tomatoes, corn, bell pepper, garlic, red pepper flakes, and salt in a large pot over medium-high heat.

Bring to a boil, and once boiling, using tongs to constantly stir the mixture. As the pasta softens, it'll get easier to maneuver.

Cook until the pasta is tender, about seven minutes. Remove from heat, stir in the cream, lemon juice and zest, parsley, and parmesan cheese. Let pasta rest for five minutes to thicken.

Taste for seasoning (if you used homemade or low-sodium broth, you'll probably want to add more salt), and then serve. Top with more parmesan and fresh cracked black pepper before serving.