I put up a post about "how to can zucchini relish", waaayyy back in 2012.... I was looking at that recipe, because I was getting desperately low on my relish supply... and I felt it needed an update.
If you want detailed instructions stop my my original post,
Canning Zucchini Relish ~ Step by Step
14 c. unpeeled, shredded zucchini
2 c. onion, shredded (If you don't want onion just add more zucchini.)
2 1/2 c. vinegar ( I used white)
1 tsp. ground nutmeg
2 tsp. celery seed
2 tsp. tumeric
4 c. sugar
1 Tbl. ground mustard
1 Tbl. cornstarch mixed with a bit of water.
Zucchini and onion soak in brine mix overnight. You may set it in the refrigerator. I usually rinse and drain while the next 5 ingredients are cooking.
Bring next 5 ingredients to a boil. Then simmer for 30 minutes. Add ground mustard, and cornstarch mixture. Cook until thicken a bit.
Add zucchini and onions and simmer for 10 minutes. Can using water bath method.