How to Make It
Combine zucchini and onions in a large nonreactive bowl. Add 1 1/4 tablespoons of the pickling salt; toss well to coat. Let stand at room temperature 1 hour.
Transfer zucchini mixture to a colander, and rinse thoroughly to remove pickling salt. Drain, and transfer to a medium bowl. Stir in celery leaves.
Divide and pack mixture evenly into 6 (1-pint) canning jars, leaving 1/2 inch of room at the top of each.
Combine vinegar and next eight ingredients with remaining 1 1/4 tablespoons pickling salt in a medium saucepan; bring to a boil over high. Reduce heat to low, and simmer 5 minutes. Remove from heat.
Carefully ladle hot vinegar mixture over zucchini mixture in jars, leaving 1/2 inch of room at the top of each. Wipe rims. Cover at once with lids; screw on bands. Cool jars to room temperature. Pickles will keep up to a month in refrigerator.