In a large bowl, mix together zucchini slices with salt. Set aside for about 20 to 25 minutes, until the zucchini slices are bendy.
Rinse the zucchini slices thoroughly under cold water at least twice. Place back in a clean bowl. Add the remaining ingredients (red onion, green onion, garlic, gochugaru, syrup, mirin, and vinegar) and stir until well-combined.
Can be enjoyed immediately or stored in an airtight container in the refrigerator for up to 10 days.