I think part of the issue seems to be the term "zionist" itself. For example, I believe in Israel's right to exist as a state, but I would not call or consider myself a zionist. Most people I know use the term zionist to refer to people who support the state of Israel in the sense of supporting THEM in their conflict with Palestine. In the same way that I wouldn't call myself a "supporter of Russia" in the context of the Ukraine war just because I support Russia's right to exist as a nation. In this context, to say I "support Russia" indicates some support for Russia's actions in Ukraine, not solely supporting the sovereign right of the state of Russia to exist. In the context of the Israel/Palestine conflict, to say you are a "zionist" to me indicates more than mere support of the right of the state of Israel to exist, but of an implied agreement with Israeli foreign policy, flauting of international law, and the continued persecution of the Paelstinian people in aid of the state of Israel.
This may just be a linguistic difference in how the term is used versus how it is broadly defined.
Yes that's the issue, we're not sure how the term Zionist is being applied by these groups. Zionism originally meant (as I understand it) support for the establishment of the state of Israel. But it has become a word, particularly on the Left, that signifies more than that. But it's not clear from the bylaw whether it would also include that idea.