Slice the zucchini lengthwise into 1/3-inch-thick slices, and then diagonally to make 1/3-inch wide batons. Drop them in a bowl, sprinkle with the kosher salt and toss thoroughly with your fingers. Transfer the zucchini to a colander set over the bowl. Let rest for no more than 30 minutes, then lift out and blot dry with paper towels.
Meanwhile, crush the garlic through a press and set aside.
Heat a big, heavy cast-iron skillet or wok over a high flame. When it’s hot enough to make a droplet of water dance, add the oil and swirl it around until it just starts to smoke. Keeping the heat as high as possible, add the blotted zucchini all at once. Spread it out in a single layer and keep it in the blazing-hot pan for 30 seconds or so to encourage some browning.
When you’re sure you see brown spots on the underside of the zucchini pieces, add in the garlic and stir-fry continuously with a slotted spoon until most of the zucchini is a mix of bright green skin and creamy flesh with golden-brown spots, and just tender. It shouldn’t take more than a minute or two. Serve immediately.