Preheat the oven to 425° F.
Roast the zucchini and chickpeas: Add the zucchini and chickpeas to a baking sheet. Drizzle with olive oil and sprinkle with cumin, garlic powder, paprika, oregano, salt, and black pepper. Toss well to coat evenly. Roast for 20-25 minutes, stirring halfway through, until the zucchini is tender and the chickpeas are lightly crisped.
Cook the couscous: In a saucepan, bring the vegetable broth to a boil. Stir in the couscous, reduce heat to low, cover, and simmer until the liquid is absorbed and the couscous is cooked. Remove from heat and stir in the olive oil, garlic powder, oregano, salt, and black pepper. Fluff with a fork and set aside.
Prepare the chimichurri: If making homemade chimichurri sauce, add all chimichurri ingredients to a bowl, jar, or food processor and mix until combined but still slightly textured. Set aside until ready to serve.
Sauté the veggies: Heat olive oil in a skillet over medium heat. Add the corn and roasted red peppers and cook for 2-3 minutes. Add the cooked couscous and cook for another 1-2 minutes, stirring occasionally.
Assemble the bowls: Divide the couscous mixture between bowls. Top with the roasted zucchini and chickpeas. Drizzle generously with chimichurri sauce and sprinkle with chopped walnuts, if desired.