Combine olive oil, lime juice, minced garlic, cayenne pepper, lime zest, black pepper, and salt in a bowl and whisk them together.
Place the mahi mahi fillets in the bowl with the marinade and turn them to ensure they are evenly coated. Allow the fish to marinate for at least 15 minutes.
Preheat an outdoor grill to medium heat and lightly grease the grill grate with oil.
Remove the mahi mahi fillets from the marinade, shaking off any excess marinade. Discard the remaining marinade.
Grill the mahi mahi fillets on the preheated grill, cooking them for about 3 to 4 minutes per side, or until the fish easily flakes with a fork and is lightly browned.
To serve, garnish the grilled mahi mahi with twists of lime zest.
If desired, you can use a lighter olive oil instead of extra-virgin olive oil.
Please note that the nutrition information provided for this recipe includes the full amount of marinade ingredients, but the actual amount consumed may vary.