It’s a good question, since they don’t taste like much. Perhaps a better way to phrase the question is: is there any advantage to putting zucchini in a sweet bread other than, you know, getting rid of another couple zucchini?
The biggest advantage is moisture. The flesh of the zucchini, as I alluded to yesterday, is mostly water. Shred it and put it in a batter and the moisture is retained in the finshed product. But then if moisture is so important why not just add more water to the batter? you may wonder. Because adding water to the batter only makes for a runny batter, one that won’t hold expanding CO2 and steam bubbles very well. The gasses just bubble right out the top before the batter can set up, resulting in a very poor rise (and usually a very tough quick bread). Zucchini flesh, by comparison, holds tightly to its water through the mixing and baking process, resulting in a very moist product — and a tender one to boot since the bits of zucchini help break up any gluten networks that may have formed in the mixing process. The same thing works with cooked potato, which like the zucchini, has the virtue of not tasting like much.
Nutritionally the zucchini is pretty much a wash. Though much is made of zucchini bread as “a serving of vegetables your kids will love” zucchini don’t pack anywhere near the vitamin, mineral and fiber punch that, say, root vegetables do. And anyway it’s not a vegetable, so why are we even having this discussion?
Zucchini do have a fair amount of vitamin A and potassium in them, as well as a good deal of manganese, which supposedly helps speed the body’s metabolism, making it burn fat faster. But then if you were really that concerned about fat, it’s probably better to avoid things like these muffins, yes?