Make the zucchini-avocado salsa: Place the zucchini, cilantro, onion, lime zest and juice, cayenne, honey, and pinches of salt and pepper in a food processor and process to form a sauce. Taste and adjust seasoning. Transfer the salsa to a bowl and stir in the diced avocado. Taste and adjust again. Set aside.
Make the black beans: Heat the olive oil in a medium saucepan over medium heat. Add the black beans and garlic and cook for 1 minute. Add the water, cumin, coriander, paprika, and a pinch of salt, and simmer for a few minutes on low. Taste and adjust seasonings and cover to keep warm.
Make the chard and leek sauté: Heat a drizzle of olive oil in a medium skillet over medium heat. Add the leeks, garlic, chard stems, and a pinch of salt and sauté for 1-2 minutes. Add the chard leaves and cook until just wilted. Set aside.
Over an open gas flame or in a skillet, heat each tortilla until a slight char forms.
Assemble tacos with the black beans, green sauté, and the zucchini-avocado salsa. Top with the cotija cheese, if using, and serve. Best served with margaritas.