Turn on the grill on high. Combine zucchini slices, olive oil, salt, cumin and black pepper in a large bowl and toss well. Grill on high, 2-3 minutes per side and set aside
Line a baking sheet or a large plate with paper towels. Heat avocado or grapeseed oil in a non stick skillet. Place one corn tortilla and cook over medium high heat, 30 seconds to a minute per side until they crisp up. Transfer to the lined baking sheet or plate and sprinkle with a teaspoon of seasoning. Repeat the process with the remaining tortillas, adding more oil if necessary
To assemble to tostada, arrange 4-5 slices of grilled zucchini on each tortilla. Place a slice of cheese on top, cover (you can use the grip cover or a heat prove bowl), lower the temperature of the grill to low and cook until the cheese has melted (time will vary depending on the grill)
Top with chopped tomatoes and garnish with cilantro. Serve warm