First of all, keep in mind this is the way I see it.
The first Musou I slayed is Guanzorumu and I think he is actually the best way to start Zenith rank or Musou monsters.
Anything, as always, feel free to leave comments with your experiences or whatever.
Music:
Zerureusu (Second phase): https://www.youtube.com/watch?v=iz9x-Klea-c
Edgar Hopp - Gravitated: https://www.youtube.com/watch?v=4-bIYDRRfD0&list=RD4-bIYDRRfD0&start_radio=1
Bye-Bye!