Heat olive oil in a skillet over medium heat; cook and stir garlic until softened, about 2 minutes. Stir zucchini, salt, Italian herbs, and red pepper flakes into garlic oil; cook and stir until zucchini begins to soften, about 5 minutes. Mix in marinara sauce and water and bring sauce to a boil.
Gently mix tuna into sauce. Simmer until zucchini are almost tender, 7 to 10 more minutes.
Bring a large pot of salted water to a boil; stir in elbow macaroni. Cook until still firm, about 7 minutes. Drain well.
Mix elbow macaroni into tuna sauce until thoroughly combined. Taste for salt levels and adjust if necessary. Turn off heat, cover pan, and let pasta and sauce stand for exactly 6 minutes and 15 seconds. Pasta will soak up the sauce and become more tender.