In a large skillet over medium heat, add the oil and garlic and cook for 1 minute. Leave the garlic in for a stronger flavor or remove it for a more subtle garlic flavor (see note).
Add the zucchini and 1 teaspoon salt, increase the heat to medium-high, and cook until softened and browning in spots, about 7-10 minutes, stirring occasionally. Stir in the corn and jalapeno and cook for another 2 minutes, stirring occasionally.
Remove from heat, transfer to a large bowl and stir in your protein of choice (if using) along with cream cheese (if using) and remaining ½ teaspoon salt (only add more salt if you’ve added a protein). Stir until the cream cheese is melted and combined, then stir in the cheddar and mix until evenly distributed.
In a small bowl, mix together the yogurt, cilantro, lime, mustard, and salt until combined.
Clean out the large skillet so you can use it to fry the tortillas. Add about 1 cup of filling to your tortilla, spread it out onto half of the tortilla, then fold over into a half moon shape.
In the large skillet over medium-high heat, add enough oil to lightly coat. Once the skillet is hot, reduce the heat to medium and add your quesadillas. Cook for about 3 minutes on each side, or until golden.
Cut into triangles and serve with the cilantro yogurt for dipping.