The second part of your definition definitely isnt true for all forms of Zionism. Zionism is as broad of a political ideology as liberalism, conservativism or communism is. Some zionists will agree with that, some won't or "soften" it to "we'll let them stay as second class citizens lol"

Zionism is essentially the belief that Ethnically Jewish people deserve their own homeland. This usually translates to "Israel has a right to exist".

This does not necessarily mean endorsement of ethnic cleansing. That is not the core of Zionism, it is the core of what you oppose, and you have been convinced to casually refer to those things as Zionism.

Taking a hard-line against Zionism in this way is like saying "Catholicism is basically the belief that women should be brood mares". Sure, Catholics are largely against Abortion, but they aren't a monolith. You're going to find plenty of members of the group that don't tow the line on that.

In this sense, you are looking at the Israeli leaders that use Zionism as a justification for what they are doing to Gaza/Palestine et al, and deciding that everyone under the Zionist umbrella must be exactly the same. The problem here is that you're dead wrong about what Zionists actually believe and are alienating people that might otherwise be your allies, because they can't tell if you're arguing that Palestine should be free, or if their friends and families in Israel deserve to be displaced, oppressed, or even murdered in revenge for the Nakba.