Bring a large pot of salted water to a boil. Add the whole wheat spaghetti and cook according to package instructions until al dente, about 8-10 minutes. Drain and set aside.
While the pasta cooks, heat the olive oil in a large skillet over medium heat.
Add the minced garlic to the skillet and sauté for 1 minute until fragrant, stirring frequently to prevent burning.
Add the diced zucchini and red bell pepper to the skillet. Cook for 5 minutes, stirring occasionally, until the vegetables begin to soften.
Add the cherry tomatoes, chopped spinach, dried oregano, dried basil, red pepper flakes, salt, and black pepper to the skillet. Stir well to combine.
Pour in the vegetable broth and cook for another 3-4 minutes until the spinach wilts and the tomatoes soften.
Add the cooked pasta to the skillet and toss everything together to combine and heat through.
Remove the skillet from heat and stir in the fresh parsley and lemon juice.
Divide the pasta evenly among four plates and serve immediately.