From Fine Cooking’s: Fresh
Wash the zucchini well to remove any grit.
Dry well and trim off the ends.
Quarter the zucchini lengthwise.
If zucchini is mature, slice off the top 1/4 to 1/2 inch of the soft seed core by running a knife down the length of each quarter; you do not need to remove every seed.
Arrange the zucchini, cut side up, on a baking sheet lined with towels.
Sprinkle with kosher salt (about 1/2 tsp per 1lb of zucchini)
Set aside for 10 minutes.
Blot zucchini dry.
Grill with your preferred marinade.
This treatment removes some of the water from the flesh so the zucchini stays firm. Don’t move the zucchini too much while cooking, it will develop a better golden exterior.