Not all anti-Zionist arguments stem from international law and the respect for human rights. Some subscribe to anti-Zionist beliefs for religious reasons.
For example, the American Presbyterian Church holds anti-Zionist beliefs not because of a respect for Palestinian human rights, but because it believes Jews "are condemned to suffer for their rejection of Jesus and complicity in his death". 
These beliefs are clearly anti-Semitic. Consequently, those who hold anti-Zionist beliefs based on purely religious beliefs are expressing anti-Semitism in their anti-Zionist beliefs. This means that in some instances, anti-Zionism is equivalent to anti-Semitism and the two have a much closer relationship with some aligned goals.