Mix chopped vegetables; set aside. Mix remaining ingredients, except water and cornstarch, in 6-quart saucepot. Bring to boil on medium-high heat. Add vegetables; return to boil. Reduce heat to low; simmer, uncovered, 15 minutes. Spoon off any foam.
Mix water and cornstarch; stir into corn mixture. Cook 3 to 5 minutes on medium heat until mixture starts to thicken, stirring occasionally.
Ladle into 4 hot sterilized pint or 8 half-pint canning jars. Cover jars with metal lids and screw on bands.
Refrigerate relish. Store in refrigerator up to 3 months.