Maybe this is a story with 8 throughlines.
Cap is MC of one throughline, Iron Man is IC of another
Steve Rogers is IC of one throughline, Tony Stark is MC of another
Zemo is Antagonist of one OC, Cap is Protagonist, IM is Contagonist
General Ross is Antagonist of another OC, Iron Man is Protagonist, Cap is Contagonist
Then there is one relationship story of Steve and Tony
And another relationship story of Cap and Iron Man.