Zucchini Relish

This recipe comes from my mom. What else would you do with 10 tons of zukes!

Zucchini Relish:
4 cups onion, diced
1 large zucchini, diced
3 red bell pepper, diced
5 Tbsp salt
6 cups sugar
1 Tbsp mustard seed
1 Tbsp dry mustard
2 Tbsp celery seed
1/2 tsp pepper
1 1/4 tsp cornstarch
Put all ingredients, except the bell peppers, into a large saucepan and simmer 30 minutes. Add the bell peppers and stir well. Cool and place in a sealed jar in the fridge, or process it.