1. Combine first 3 ingredients in a large bowl. Add 2 teaspoons salt; toss well. Let stand 20 minutes. Transfer vegetable mixture to a colander. Rinse well with cold water; drain well.
2. Combine remaining 2 teaspoons salt, sugar, and remaining ingredients in a large bowl. Add vegetable mixture; stir well. Transfer to an airtight container, and refrigerate for at least 2 days before serving.