Dang, that's a small zucchini - was my first thought. But then, people don't believe we have grapefruit as big as your head, either. California backyards produce some weird results. Might be all the air pollutants causing mutant fruit. My friend's lemon tree (about a hundred years old, she has a house on the local register of historical homes) has lemons that are big as footballs.
When I was a kid we had zukes in our garden - the plants would get huge and then the zukes would hide out in the leaves until they got huge and tough. Once in a while they got bigger around and almost as long as my baseball bat. Never thought of using them on bears, or anything else.... Bet that bear got a real knock on the noggin, those things are pretty dense.