the figures during the war were probably not missing 6 million people as we did not find out the full extent of the Nazi genocide until after the war. By 1951, one would expect a somewhat accurate deathtoll, and thus new publications with a diminished Jewish populations would be accounting for that data.
I don't see the benefit in using the word 'Zionist'. Zionists are people who believe the Jews should go back to Israel or something. what does that have to do with people dying in WW2?
We know the deathcamps killed people. We have some air reconassiance photographs showing the furnaces and gas chambers on them.
It is fact that the Nazis had a 'euthanasia' program for the disabled. How is it hard to imagine this would be extended to the deathcamps, in order to kill homosexuals, atheists, freemasons, political dissidents, Gypsies, Jews, Slavs, Poles, and Soviet POWs?
and there were some deathcamps outside of the post-war Warsaw pact. A small one was set up in Italy late in the war., for example. True, most were in Poland. But, if the deathcamps were said to be in Soviet territory, why would they not say deathcamps were in Czechoslavaki, or Romania?
There is documentation of genocide, here is an example of something I saw

Note how it says 'Judenfrei' in Estonia. Perhaps this was just one crazy soldier, who somehow had information on how many Jews were alive in Poland, Estonia, Latvia, and Lithuania. Perhaps it was bigger than that.
edit: Also note that that picture was probably irrelevant to the big picture