Wash and finely chop the zucchini, tomatoes, onion, and green bell peppers. Set aside.

In a large pot, combine the chopped vegetables and cook over medium heat for about 10 minutes, stirring frequently.

Once softened, add vinegar, sugar, salt, ground cumin, crushed red pepper flakes, and black pepper to the pot. Stir well.

Reduce the heat to low and let simmer for 20-25 minutes, stirring occasionally to prevent sticking.

Stir in chopped cilantro before removing from heat. Let cool slightly before canning.

Ladle salsa into sterilized canning jars, leaving about 1/2 inch of headspace.

Wipe the rims of jars and seal with sterilized lids and metal bands.

Process jars in a boiling water bath for 15 minutes.

Remove jars and let cool undisturbed for 12-24 hours to create a vacuum seal.