Combine the zucchini, onions, peppers and garlic in a large bowl. Stir in the salt, then cover the whole bowl with cracked ice. Cover with a heavy towel and let sit for 2-3 hours.
Get 8 pint jars, lids and rings prepared.
Drain the vegetables and put them in a large pot.
Mix the sugar, turmeric, mustard seed and vinegar and pour over the vegetables.
Bring to a boil, stirring, then put into the pint jars.
Load the jars into your kettle and process for 10 minutes.