From 2:00 to about 8:30,
In these 6 and a half minutes rhythm guitars are relentless through and through, this is the most complex part Maiden has ever done with riffs. The downpicking pattern is ~ 350 bpm over the staccato parts and apart from easing into ringing/stabbing chords every now and then, there is no rest point to it and the groove is that deep in the pocket it's impossible to follow through without practice.
It reminds me of the interplay between bass drums and rhythm guitar in last part of Seventh Son's breakdown. When Smith starts chugging. You can see his concentration live, it's hard to lose those accents. In Parchment it goes for minutes...
Just try the last part ("in a tempest never shaken"), it's basic E-C-A-B, you'll see what I mean by the time you reach half of it.
My god would I want to get stems for this one and remove or adapt the synths, the guitar work is immense.
It's also hard for me to judge the entire song as this part is probably something best Maiden have ever done.
For me it's competing with Seventh's Son's instrumental part for the best written metal arrangement of theirs.