Heat a large skillet on medium-high heat. Add the oil and add in the zucchini, 1/2 the red onion, minced garlic and corn kernels. Cook for 8-10 minutes until crispy. Season with salt and pepper.
In a small bowl, mash the avocado with lime juice, zest, remaining red onion and jalapeno. Season to taste with salt and pepper.
Divide the avocado in 1/4 and smash onto warmed tortillas.
Top with zucchini mixture and garnish with cilantro and queso fresco