Heat a layer of olive oil in a skillet over medium high. When the oil begins to shimmer, add the zucchini in an even layer, avoiding overlapping in the skillet (you may need to cook in batches to avoid overcrowding!). Season with salt and pepper. When the zucchini begins to brown on the bottom, about 5 minutes, flip over and allow to brown on the other side, about 4 minutes more. Remove from the skillet to the serving plate.
Meanwhile, make the pesto. Add the walnuts, basil, mint, Parmesan, vinegar and a pinch of crushed red pepper to the carafe of a food processor. Pulse until the ingredients are combined but still chunky. Taste and season with salt and pepper as needed.
Drizzle the pesto on top of the zucchini. Top with additional Parmesan, fresh basil and crushed red pepper flakes and serve!