At least 4 hours before you’re ready to make the pancakes (or the night before), shred the zucchini using a grater. Bundle the shreds into a clean kitchen towel and place in a colander set over a large bowl. Salt the zucchini evenly and then weigh down the zucchini with a heavy plate or bowl. Place the whole thing in the refrigerator and let the zucchini drain for at least a few hours (or overnight).
When ready to cook, heat the butter in a cast-iron skillet (or your favorite pancake skillet/pan) over high heat. Preheat the oven to 200F (optional, it’s just to keep the pancakes warm). Prepare the pancake mix according to the package, adding the sugar last. Pat the zucchini dry to remove remaining moisture, then gently mix it into the pancake batter. Stir slowly until the zucchini is well dispersed.
Add the zucchini batter to the pan in spoonfuls, making sure to fry only a few at a time so as not to crowd them. Let the pancakes cook for 3-4 minutes on each side. As they are done cooking, pile them on an oven-safe plate or sheet pan to keep them warm as you cook.
Serve with maple syrup and Greek yogurt. This makes around 10-12 pancakes, depending how large.