I put it (and all forms of summer squash) in the veggie part of the raw/home made diet I feed. It is totally fine as long as your dog isn't sensitive to it specifically (like anything else). We feed it cause we get all of our veggies from the farmers market and it is FILLED with summer squash these days!
We eat it at this time of year and sometimes if I make some, I put a bit of it in her kibble. She really likes it but I havent given it to her raw. Its not unsafe per se, but like all new foods you dont know what they can be allergic to and what not.
Well, I gave them some, I peeled it first. Guillermo loved it, but Chica would have nothing to do with it. She used to like carrot sticks but I can't get her to even eat those anymore. She does nit like her veggies!
Go for it! You can give it sliced in "stick" shape for them to eat like a bone, or puree it up and put in with the food (raw). Remember the rule of veggies and dogs....
Above ground grown vegetables are loosening to the stools and below ground grown veggies are firming to the stools.
If you keep that in mind, any veggies are fine (pureed ones are better absorbed for nutrient value, but chunks are fun treats to chew) just adjust your bone content if feeding raw, or add canned pumpkin to kibble if they ate too much above ground veggies (your zucchini) . Enjoy