Anti-Zionism can mean opposition to Israel’s existence as a Jewish state, opposition to a particular expression of Zionism, or criticism of Israeli policy. Criticism of a government addresses its decisions; denying Jews, as a people, national self-determination rejects a right recognized for peoples generally.
What international texts say
Article 1 of the International Covenant on Civil and Political Rights says all peoples have that right and may freely determine their political status.
Jewish national identity and connection to the Land of Israel long predate the modern political movement. Zionism emerged in the 19th century as a movement for Jewish national revival and statehood. Israel’s Declaration of Independence in 1948 declared the establishment of a Jewish state. The IHRA working definition lists denial of Jewish self-determination, including claims that Israel’s existence is a racist endeavor, among examples of antisemitism.
Distinguish political proposals from group denial
Israel’s laws, borders, government, and constitutional arrangements are subjects of political debate. Proposals for equal civil rights or a shared political arrangement must protect the safety, rights, and political participation of Jews and other residents. Advocacy of expulsion or violence, or rejection of Jewish national expression while accepting comparable national aspirations elsewhere, denies Jews equal rights.
In his 3D framework, Natan Sharansky describes double standards as one of three forms of anti-Israel rhetoric associated with antisemitism. Article 1 of the Covenant affirms self-determination for all peoples, and the IHRA examples identify denial of Jewish self-determination as antisemitism.
For a practical framework on particular language, see how to tell criticism from antisemitism. For examples of anti-Jewish myths appearing in arguments about Israel, see antisemitic tropes applied to Israel.