Place olive oil, lemon juice, orange zest, garlic, salt and pepper in a small bowl and whisk together.
Thread the beef strips onto the skewers. If using wooden skewers, be sure to soak them in water so they do not burn on the grill.
Place the skewered beef into a flat dish and cover with the marinade. Marinate the meat for at least 4 hours or overnight.
Pulse the mangoes in a food processor. You want the mangoes to have a little texture and not be too runny.
Combine olive oil, lemon juice, rice vinegar, harissa, red pepper, parsley, cilantro and scallions with the mangoes. Salt and pepper as needed.
The chutney can be stored covered in the refrigerator for 1 week or frozen for several months. This chutney can be canned and enjoyed all year long.
Preheat the grill to medium heat, or if you are cooking indoors preheat a grill pan to medium high heat.
Combine the sumac, coriander, black pepper, cumin and salt in a small bowl. Sprinkle the skewers with the spices.
Place the skewers on the grill and brown them before turning about 3-5 minutes. Brown the other side and remove to a serving platter.