To season chicken and shrimp: In large bowl, toss chicken and shrimp with fajita seasoning. Add lime juice and lime zest. Toss and set aside.
To stir-fry vegetables: In large skillet, bring 2 tablespoons oil to a sizzle. Add garlic, pepper and onion. Stir-fry for 4 to 5 minutes or until vegetables are soft and slightly charred. Remove to plate.
To cook chicken and shrimp: Wipe out pan. Add remaining oil. Heat over medium-high heat until oil sizzles. Add chicken and shrimp. Stir-fry for 3 to 4 minutes or until shrimp is pink and chicken is crispy brown. (Note: If you're worried about overcooking shrimp, cook separately.) Season with salt and pepper. Return vegetables to pan. Stir. Reduce heat to keep warm.
To prepare beans: Rinse and drain black beans. Heat in microwave or on stove top until warm.
To assemble: Place 1 cup rice in bowl. Squeeze a little lime juice on top. Spoon on 1/2 cup beans. Add one-quarter of chicken/shrimp mixture and shredded cheese. Add topping as desired.