Why is there a switch in gender in the pronoun in the second clause? I get why the pronoun is feminine in the first clause (because אגדה is feminine), but why does it become זה in the second clause?
Maybe the subject of the second clause is not a legend but a story סיפור and it is a masculine word, so it is זה. This story is not a legend, it is real. הסיפור הזה לא אגדה, זה אמיתי.