Place the sliced zucchini in a bowl or jar. Heat the remaining ingredients in a sauce pan until the sugar is dissolved. Pour the liquid over the zucchini and set aside.
Combine the brown sugar, soy sauce, sesame oil, gochujang and ginger powder in a bowl. Stir and set aside. Heat the oil in a pan over medium heat. Add the onion & garlic and cook for 3 minutes, or until the onion is slightly tender. Add the lentils and beef crumbles and cook for a couple more minutes. Pour in the sauce, lower the heat and cook until the sauce has thickened and been absorbed.
Heat the tortillas over an open flame. To assemble, layer each tortilla with the vegan beef, cabbage and pickled zucchini. Drizzle on spicy mayo and top with green onion.
*For spicy mayo: combine 2 parts vegan mayo, 1 part sriracha and lime juice to taste.