Preheat oven to 400Mix lemon zest, olive oil, and salt and pepper in a bowl. Marinate mahi mahi for 5-8 minutes.While fish is marinating, bring 2 cups of water to a boil. Add couscous, cover and simmer 10-12 minutes.Mix all mango salsa ingredients together in a bowl and place in the fridge until ready for use.Take fish out of marinade and place on a greased baking sheet. Place in oven for 8-10 minutes.Once fish is done, place on a plate and cover with mango salsa and serve with couscous.