Kernels cut from corn cobs, about 4 cups. chile: stemmed and finely chopped kirby: trimmed, seeded, and chopped bell pepper: cored, seeded, and chopped zucchini: trimmed and chopped
Heat butter in a medium pot over medium heat. Add onions and garlic and cook until just soft, 3–4 minutes. Add corn, chiles, cucumbers, peppers, and zucchini and cook, stirring occasionally, until heated through, about 2 minutes. Add vinegar, mustard, curry powder, dill seed, and cumin and bring to a boil, stirring occasionally.
Meanwhile, put flour and 2 tbsp. water into a small bowl and stir into a paste. Add flour paste and sugar to pot and cook, stirring occasionally, until relish has thickened slightly, 5–7 minutes. Season with salt to taste.
Transfer relish to a large bowl and let cool. Store, covered, in the refrigerator for up to 7 days. Serve on toasted wheat bread, spread with butter and mashed avocado, if you like.