If using wood or bamboo skewers, soak them in water while you prepare the ingredients.
In a large bowl (5-quart) or dish combine all the ingredients for the Chimichurri sauce: finely minced parsley, finely minced fresh oregano, 3/4 cup corn oil, lime juice, red wine vinegar, minced garlic, minced red onion (take a bit from the skewers), salt, and red pepper flakes. Mix well. Set aside half into a small serving bowl - this will be the sauce.
Slice the zucchini. Clean the bell peppers and cut them into 1-2 inch squares. Cut the red onion into quarters and then into 1-2 inch pieces (see photo in blog post). Add the shrimp and chopped vegetables to the large bowl containing half the marinade (don't forget to set half aside so it's not contaminated by raw shrimp!). Mix well. Allow to marinate for 20-40 minutes, or up to 2 hours.
Preheat the grill to high heat, to at least 300F. While the grill is preheating, place the shrimp and vegetables on the skewers, aiming for about 2-3 shrimp per skewer. (You can also do this in advance)
Place the skewers on the preheated grill and cover. Allow to cook undisturbed for 5 minutes. Use grilling tongs to carefully flip the skewers, cover, and continue to cook for 5 minutes, or until the shrimp is fully cooked.
Remove from heat and serve warm with the remaining chimichurri sauce on the side.
Use the largest shrimp you can find, 16-20 count per lb or bigger is a nice size. Use thin zucchini, or slice a thick zucchini in half lengthwise so the zucchini is not much wider than the shrimp.