This is absolutely a delicious combination with hamburgers which you definitely need to try. Here’s how to make it: 

Ingredients:

• 12 cups shredded unpeeled zucchini
• 5 tablespoon non-iodized salt
• 4 cups chopped purple onion 
• 1 chopped red bell pepper
• 1 chopped green bell pepper
• 6 cups white sugar
• 2 ½ cups white vinegar
• 1 tablespoon cornstarch
• ¾ teaspoon ground turmeric
• ¾ teaspoon ground nutmeg
• ½ teaspoon ground black pepper
• 1 ½ teaspoon celery seed

Steps:

• Place the onion and zucchini in a large non-metallic bowl, and sprinkle the salt. Use your hands to mix the salt throughout evenly. 
• Cover and refrigerate overnight.
• The next day, drain the zucchini in a colander and rinse thoroughly with cool water. 
• Squeeze out excess water and keep it aside. 
• Put the green and red bell pepper, vinegar, sugar, and cornstarch into a large pot, and add the nutmeg, celery seed, turmeric, and pepper.
• Stir to combine, then add the drained zucchini. 
• Bring it to a boil over medium-high heat. Then reduce to low heat and simmer for 30 minutes.
• Meanwhile, sterilize seven 1-pint jars and lids to hold relish. Pack relish into sterilized jars, ensuring there are no air pockets or spaces. 
• Fill jars all the way to the top and screw the lids on.
• Place a rack in the bottom of a large stockpot and fill halfway with boiling water. Carefully lower jars into the pot using a holder. 
• Leave a 2-inch space between jars. Add more boiling water till the top of the jar is covered by two inches of water. 
• Bring water to a full boil, cover and process for 30 minutes.
• Remove jars from pot and place on a wooden or cloth-covered surface, several inches apart from one another until cool. 
• Once cool, press the top of each lid with a finger, ensuring that the seal is tight.