Take the bavette out of the refrigerator half an hour before cooking. Meat at room temperature cooks much more evenly than meat that goes into the pan cold.
Make the chimichurri by finely chopping the parsley, oregano, and garlic, and mixing them with three tablespoons of olive oil, the red wine vinegar, the chili flakes, and salt. Let the sauce sit while you continue cooking, so the flavors can infuse into the oil.
Preheat the oven to 200 degrees. Cut the sweet potato into wedges, drizzle with the remaining olive oil and salt, and roast for twenty-five minutes. Slice the zucchini lengthwise into thick slices.
Season the bavette generously with salt and pepper and sear it in a smoking hot grill pan for three minutes per side for medium-rare. Then place it on a board and let it rest under foil for five to eight minutes; if you slice it too early, all the juices will run out. Grill the zucchini in the same pan for two minutes per side.
Slice the bavette across the grain into thick strips, place them on top of the vegetables, and generously spoon the chimichurri over them.