Heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray.
Add onion, and saut 5 minutes.
Add zucchini and bell pepper, and saut 3 minutes; stir in curry paste.
Add chicken, broth, and coconut milk to pan; bring to a boil. Reduce heat, and simmer 3 minutes. Spoon evenly into 4 bowls; sprinkle evenly with cilantro.
Serve with lime wedges, and garnish with cilantro sprigs, if desired.