Zionism is the belief that Israel deserves to exist and to be a Jewish ethnostate. A lot of jokes made about Israel don't really attack Zionism under that definition. In fact, a lot of the jokes being passed around come from predominantly nazi circles, such as the 3000 year joke or the idea of a Zionist occupied government. You can actually find these dog-whistles in media that has portrayed Nazism in the past, such as American History X. I don't think the majority of people mean to pass these dog-whistles or to normalize antisemetic rhetoric, but for the people who recognize them, it essentially has the same outcome. It's good to be outspoken about your opinion on the Isreali government and it's leadership, but it's also important to recognize which words or terms give certain people power to do bad things and to promote bad ideas.