It is counterintuitive but it does make sense. You see the initial plan the Nazis used to try to get rid of the Jews was to expel them from Germany. They had no problem if the Jews all grouped together and settled their own country so long as it was somewhere else. Far away from them. (And when they didn't leave they made conditions horrible for them). That's why antisemites love Zionism; it's a way to get rid of the Jewish population in their country without dirtying their hands with ethnic cleansing. Which is how we get to conspiracy nutjobs who rant about Jewish space lasers setting forest fires in the US for some reason, turning around and enthusiastically supporting Israel and defence aid for Israel.

https://en.wikipedia.org/wiki/Zionist_antisemitism

To put it briefly. Zionism is a ethno-nationalist ideology. One country for each ethnicity and were the dominating ethnicity gets to supress every minority. This on the one hand is what whit supremacist fascists believe too. On the other hand Israels key claim to its right to exist at the genocide and ethnic cleansing of Palestinians is that Israel would be the only safe place for Jews in the world. If Jews are persecuted and discriminated against outside of Israel this is good for Israel as they can justify their existence with it. For Antisemites historically and today it is great to allow for an out to "get rid of the Jews" by sending them to Israel. Exactly what was done by Britain.

So they both share the same ideological core, which is ethnostates ("Blut und Boden" - blood and soil, like the Nazis called it) and operatively they profit from each other.