Add the chopped zucchini, onions, and bell peppers to a large bowl.

Sprinkle with salt and mix well. Cover and refrigerate overnight to draw out excess moisture.

Drain the zucchini mixture in a colander. Rinse well under cool water to remove excess salt. Press firmly to remove as much liquid as possible, then set aside.

In a large pot, combine the vinegar, sugar, horseradish, ground nutmeg, turmeric, and chopped hot chili pepper.

Add the drained vegetable mixture and stir to combine.

Bring to a boil over medium-high heat, then reduce the heat to a gentle simmer.

Cook uncovered for about 45 minutes, or until most of the liquid has evaporated and the relish thickens. Stir occasionally to prevent sticking.

Place the water bath canner on the stove and add the rack.

Arrange clean jars upright on the rack.

Fill the canner with water to cover the jars.

Warm over medium heat (180˚F), and simmer for at least 10 minutes. Keep warm as you fill your jars.

Lay a clean towel on your work surface.

Use a jar lifter to remove a warm jar from the canner. Drain the water back into the canner, and place the jar on the towel. Keep the remaining jars in the canner so they stay warm.

Remove air bubbles with a bubble popper and adjust headspace if needed.

Wipe the rim clean, center a lid on the jar, and screw on a band until fingertip tight.

Return the jar to the canner, then repeat with the remaining jars.

Make sure the jars are covered by at least 2 inches of water.

Cover the canner and bring to a rolling boil.

When the processing time is complete, turn off the heat.

Remove the lid and let jars rest in the canner for 5 minutes.

Spread a dry kitchen towel on the counter.

Use the jar lifter to lift the jars from the canner and transfer them to the towel-lined surface. Keep the jars upright, and don't tighten bands or check the seals yet.

Let the jars sit undisturbed for 12 to 24-hours to cool.

Check the seals after the cooling period. Any unsealed jars should be refrigerated and used within a month.

Remove the screw on bands and wash the jars in warm soapy water to remove any residue.

Label and store sealed jars in a cool, dark place for 12 to 18 months.

Allow at least 3 to 4 weeks for the relish to develop its flavor. Once the jar is open, refrigerate and use up within a month.