Freshly chopped mint is used frequently in Greek cuisine and can be a great substitute for dill in this vegan tzatziki. It has a refreshing and slightly sweet flavor that pairs well with the other ingredients. Flat leaf parsley has a mild, fresh flavor that complements the tanginess of the yogurt perfectly. Cilantro has a slight citrusy flavor that can add a zing to this tzatziki sauce, but use it sparingly as it can be overpowering. Finally, although not traditional in tzatziki, fresh basil can be a flavorful herb to use as a substitute for the dill in this recipe.