Combine tomatoes, onion, zucchini, serrano, garlic, lime juice, and salt in a large bowl. Transfer to a fine mesh strainer set over a bowl and allow to drain for 20 minutes.
Return the vegetables to the bowl. Add cilantro, parsley, masa harina, flour, baking powder, coriander, panko, and queso fresco. Season with black pepper and mix until evenly combined.
Let the mixture sit for 20 minutes. This gives the flour and masa harina time to hydrate and helps everything hold together.
The mixture should feel moist but still hold its shape when pressed together. If it's too loose, add additional flour one tablespoon at a time.
Heat peanut oil to 350°F (175°C) in a heavy-bottomed pot or high-sided skillet.
Divide the mixture into 10 portions. Form patties and make a slight indentation in the center of each one.
Working in batches, fry for 2–3 minutes per side until deeply golden brown and crisp. Avoid overcrowding the pan.
Transfer to a paper towel-lined tray or wire rack. Season lightly with salt while still hot.
Add the queso fresco and Greek yogurt to a food processor. Pulse until combined.
Scrape down the sides. With the machine running, slowly drizzle in the olive oil. Process until smooth and creamy.
Taste and adjust with salt as needed.
