https://i.stack.imgur.com/yQU9l.jpg What does the ぞな mean here? I thought it could be a masculine emohasis. But it's also used with な.
This is a prototypical Iyo dialect populaized by Soseki's bestselling novel, to the point that it's disproportionately well known to Japanese people compared to the population who actually speak the dialect, which is dying.
I don't think Kiyohiko Azuma, the writer, specifically set an Iyo (Ehime) background for this old lady. (He is not known for doing that kind of detailed research.) My guess is he simply found the sound of the dialect interesting and wanted to create an exotic atmosphere by having the lady speak it.
Online sources suggest that ぞなもし breaks down into ぞ + な + もし where もし is probably synonymous with 申し (as in 申します). In any case, the local Iyo people are known to add this word to the end of sentences to mean "isn't it?" or "don't you think?".