How to Make It
Place zucchini and onion in a large bowl. Sprinkle with salt, and toss to combine. Let stand 10 minutes. Pour in a collander, and rinse with cold water. Divide zucchini mixture into 2 (1-quart) jars or containers.
Combine vinegar, water, sugar, mustard seeds, celery seeds, peppercorns, turmeric, bay leaves, and garlic in a medium sauce pan, and bring to a boil over medium-high. Reduce heat to medium, and cook, stirring occasionally, until sugar is dissolved, about 3 minutes. Pour hot vinegar mixture over zucchini and onion, and let stand 10 minutes. Seal with lid, and refrigerate overnight.