>>This is the reason why, according to Zeiri, the Chachamim did not prohibit the maternal side even though the paternal side is prohibited. Accordingly, the wife of one's mother's father is not prohibited. The Gemara earlier discusses the opposite situation -- prohibiting the paternal side because the maternal side is prohibited. If one's mother's mother is prohibited, then the Chachamim should also prohibit one's father's mother because the paternal side is always treated more stringently due to the higher degree of closeness one feels with his relatives on the paternal side.<<

I think the underlined part should be 'the wife of one's mother's father's father." Even Zeiri agrees that one's mother's father is prohibited as one of the shenios. He just holds that there's hefsek.

Thanks,

Nathan Hyman