Wash the potatoes and cook for about 20 minutes. Drain, let cool a little, peel. Then cut into slices, salt and pepper.
Wash the lemon, dry it and rub the peel. Squeeze out the juice, mix 4 tablespoons with the broth and mix with the potatoes. Peel the cucumber, cut in half lengthways and scrape out the seeds. Cut the cucumber into slices and add to the potatoes. Cut the onion into small cubes, grate the radishes and mix everything with the potato-cucumber mixture.
Chop the coriander, chives and parsley, mix with the yogurt and lemon
Mix in the zest, season with salt, pepper and pour over the salad, mix and refrigerate.