Meanwhile, spritz a pie pan (8 - 9 inches) with nonstick spray. Arrange 2 layers of the crackers on the bottom. Break extra crackers to use on the sides of the quiche (if desired) and arrange along the sides. It's not necessary to cover 100% of the pie pan, but you can use broken crackers to fill in any large gaps.
Allow the veggies to cool slightly. Pick out the zucchini slices and arrange on top of the crackers. Spoon out an even layer of the remaining veggies.
Top the veggies with ¼ c cheddar cheese.
Whisk the eggs and yogurt, adding salt and pepper to taste, until well combined.
Carefully pour the eggs over the vegetables. Arrange tomato slices on top.
Bake for 20 - 30 minutes on the bottom rack in the oven until the quiche is set. It shouldn't jiggle when you shake it.
Allow to cool at least 15 minutes before slicing.
Notes
Serves 4 as a large main dish (I served with a salad) or 8 as a part of a large brunch. The vegetables can be swapped out to your preferences, but be wary of adding too much liquid from raw veggies -- I recommend cooking in advance. I have only tested Breton Gluten Free Original with Flax Crackers in this recipe -- because crackers are relatively unique, I cannot recommend any other type accept a like-for-like swap (i.e., subbing in the Herb and Garlic flavor).
After baking, the crackers on the edge will be crisp like fresh from the package, the bottom layer will have a little more of a softer, pie-crust type texture.