I definitely agree that Mazin Kenzan is probably one of the best insert songs there is in anime. The energy/ vibe is overpowering and sets the stage for one of the most epic fight scenes not only in mazinkaiser v. the great general of darkness but in the entire series, inclusive of all the other alternate versions that's been produced so far. It's just ironic that these versions of Mazinger's story (Mazinkaiser and Shin Mazinger Edition Z: the Impact) actually tell the story of mazinger better than the titular/original version (1970s). It's well known that Nagai left Toei and went on to establish his own studio. Still, Mazinger and all related stories are epic in their own right... and seem to be canon for hardcore and casual fans alike.