Heat 1 tbsp olive oil over medium; add garlic, bell peppers, and zucchini and cook 3–4 minutes until peppers soften and zucchini starts to turn golden around the edges.

Stir in penne pasta and pour 4 cups vegetable broth; bring to a gentle boil, scraping brown bits from skillet for extra flavor.

Reduce heat to low, cover, and let simmer 12–15 minutes, stirring halfway, until pasta is al dente and most broth is absorbed, with a creamy cooking liquid.

Lower heat to medium-low, drop in cream cheese; stir until smooth. Add shredded mozzarella and Parmesan, stirring constantly until cheese is ooey-gooey and fully melted.

Fold in spinach until wilted, then sprinkle Italian herbs and red pepper flakes. Taste and adjust salt & pepper to your liking before serving.