This is a great way to use up all of that summer zucchini!
Put zucchini, scrubbed and trimmed, through the coarse blade of a food grinder to measure 12 cups (we use the grater attachment of our cuisinart).
Pass the onion through the same process, until you have about 4 cups.
In a large ceramic or glass bowl combine the zucchini, onion, and 5 tablespoons pickling salt, and chill the mixture, covered, overnight.
The next day, drain the zucchini mixture in a colander, rinse it under running cold water, and drain thoroughly.
In a kettle or large stock pot, combine the sugar, cider vinegar, dry mustard, celery seed, pepper, and turmeric and bring the liquid to a boil, stirring until the sugar is dissolved.
Add the zucchini mixture and 2 sweet bell peppers, both chopped fine, and simmer the mixture, stirring frequently, for 30 min.