I don't intend to get into a protracted debate about the difference. Many people have already done so. Here are some examples:

Alan Hart "Zionism: The Real Enemy of the Jews" (book - on the Web)

"Jews Against Zionism" (website) 

Neturei Karta True Torah Jews (website)

Here is the key point:

Real Jews worship Yahweh. They try to follow His Commandments. One of them is: "Thou shalt not kill"

Zionists worship Satan, the "god of this world", in the "Synagogue of Satan" (that's an old story but still true). They murder anyone in their way without any qualms. Deception is their trademark (Mossad).

Zionists have USURPED Judaism and deceived most of Jewry. There are only a few thousand Satan-worshiping Zionists vs millions of Jews. Many Jews oppose Zionism (even in Israel) but they are intimidated against doing so by being accused of being 'self-hating' Jews and being threatened with ostracism from the Jewish community. Many protest against Zionism despite these threats! :)

Zionists have also deceived millions of so-called 'Christians', led by ZioChristians like John Hagee, Pat Robertson and many others (CUI).

The actions of Israeli Zionists (leaders) towards Palestinians (and Rachel Corrie, et al) and in general, reflect callousness, inhumanity and deception (Dimona) - and  MANY 'false-flag' Ops against Americans (USS Liberty, 9/11, etc.) and humanity do the same.

Humanists should be defenders of human rights against all those who abuse humanity and human beings - like Palestinians! Aren't they human, too?!

Perception is NOT reality!

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We hold these truths to be self-evident...."