https://en.wikipedia.org/w/index.php?title=Vegetable#Terminology
Posting this link again because you didn't read it.
Culinary vegetables unarguably exist since we're referring to a physical thing which indisputably exists. I have seen a courgette before, I can confirm vegetables do in fact exist. You're arguing that they don't exist because you disagree with the words used to refer to them, which is also wrong. The fact many people use the culinary definition of vegetable when referring to courgettes means that the culinary definition of vegetable is correct; language is defined by how it's used.
Vegetables exist. The culinary definition of vegetable also exists. The fact you don't like that definition is irrelevant.
You clearly didn't bother to read anything I wrote (or you completely lack reading comprehension), but I'll give it one more shot.
https://en.wikipedia.org/wiki/Zucchini
https://www.merriam-webster.com/dictionary/vegetable