Peel the washed potatoes and zucchini, dice them, and put only the potatoes in to boil. Meanwhile, cut the onion in a deep bowl into slices.
Once the potatoes are tender, add the zucchini. Once ready, carefully drain them and put the onions in. Toss the salad with olive oil and mayonnaise. Add a pinch of white pepper and finely chopped dill.