Learn Farsi: نام‌برده مظنون اصلی پرونده‌ی مذکور است. - The said person is the main suspect of the aforementioned case.

Here, nâm-borde acts as a standalone pronoun meaning "the said person" or "the aforementioned." While it literally means "the one whose name was mentioned," it is almost exclusively used for people in formal, journalistic, or legal contexts. You wouldn't use it to refer to a previously mentioned object.

How does mazkur differ from nâm-borde, and could I swap them in this sentence?

You cannot swap them. While both translate to "aforementioned," mazkur is standardly used for inanimate objects, places, or abstract concepts (like parvande, meaning "case" or "file"). Also, notice that mazkur is acting as an adjective here, attached to parvande with an ezâfe, whereas nâm-borde is acting as a noun/pronoun.

Could you break down the ezâfe chain in the middle of the sentence?

The phrase is maznun-e asli-ye parvande-ye mazkur. The first ezâfe links the noun maznun (suspect) to its adjective asli (main). The second ezâfe (-ye, since asli ends in a vowel) links that entire phrase to the next noun, parvande (case), acting like the English word "of". Finally, the third ezâfe links parvande to its adjective mazkur (aforementioned).