How is どこぞの is being used in this sentence?


[![enter image description
here](https://i.stack.imgur.com/EyZGy.png)](https://i.stack.imgur.com/EyZGy.png)

I understand どこぞ is "Someplace/somewhere" and a の adjective, but how it's
actually modifying 力自慢?




The particle の here indicates the location (e.g. 大阪の友人 "the friend (who is
located/ who lives) in Osaka,") so the literal meaning is "力自慢 who is located/
lives somewhere". どこぞ has a vaguer nuance than どこか, so it can be simply
translated as "the (said) 力自慢", if context allows.

