Prof, the Gemara does say that but we do not pasken it. In any case, according to the position of the gedolim you cited only secular Zionism would be apikorsut. The question is what they would think of frum Jews who prevented Israel’s establishment as a Torah state by not coming when they could.
Akuperma, if one holds that it is an aveira to establish a Jewish state in EY someone who supports Zionism because of various advantages is a mumar l’teiavon. According to your definition of apikorsut If you hold that it is a mitzva anti-Zionism is apikorsut. Of course, one could simply say that it is a legitimate machloket and neither are apikorsim.