In a large saucepan or Dutch oven, cook the onion in oil until tender, but not brown. Add zucchini. Cook and stir until the vegetables begin to brown.
Add salsa, broth and spinach. Bring to boiling. Add the tortilla chips and stir to coat. Remove from heat. Cover and let mixture stand for 5 minutes.
Very carefully stir the mixture to check that the chips have softened nicely. (Rick prefers them to have a few chewy edges. If there's still too much crunch remaining, the chef dribbles in a little extra broth and returns the mixture in saucepan to heat for a few minutes.)
Sprinkle with cheese. Serve from the pan. Or you can spoon mixture onto warm plates or into shallow bowls in the kitchen before sprinkling with cheese. Makes 4 to 6 main-dish servings.