Its absolutely not. Neither is suggesting (for example) that Israel is committing war crimes. But you can be extremeky critical of Israel and still think it has a right to exist, in line with long-stamding US foreign policy and the U.N efforts to find a two-state solution. Anyone who supports a two-state solution is a Zionist, by the dictionary definition. And that includes Biden - and me.
The difficulty is that the term 'Zionism' comes wiith a lot of extremely unpleasant shit associated with it.