Why did Zionists refuse to help Jews during the holocaust, stating they required "many human sacrifices"?

Because the Jews too are human--perhaps more so than any other nation--and are thus subject to extremism, self-contradicting theories, and legalism. There is quite a bit of good in the Zionist movement, but there are also a lot of negative things about it, one being their tunnel vision, another being their exclusive (and, quite frankly, racist) attitude.