Hmmm, I've been told that Parts 6 and 7 are boring.  Hell, I found _myself_ yawning while reading.  Parts 6 and 7 are a tangent to the core story. Feel free to skip them.  They are about how the strange three-way romance between Noin, Zechs, and Une developed.  (And, yes there's yuri, and if I remember correctly,  there's either some three way fondling or kissing in part 7 somewhere).  Anyhoo, when I remember, I will post summaries for parts 6 and 7 since they are so freaking long.  -_- 

If you would like to actually read or skim these parts, here they are: Part 6   Part 7

And, if you like to skip, here's Part 8