In a measuring cup add the zest and lemon juice. Add olive oil, salt, and pepper. Taste and adjust. Should be tangy and acidic, not too oily.
Shave the fennel paper thin -- easiest with a mandoline even if you factor in the injuries. Large slices you may want to break or cut in half. Add to a large bowl.
Add the mint and and toss to distribute. If using, add the cheese and dill.
Re-mix the dressing and drizzle over the salad, tossing to coat.