So this is a question I've seen many times with different bakes - whether or not you're meant to peel the vegetable or fruit before using it. For this bread, there is no need to peel the zucchini first and it can be grated with the skin on. I would normally recommend cutting the end off first and then grate by holding the stem. Once you've grated the full zucchini, you can then discard the stem.