I also think the storyline was confusing from ZX, and also the transition to ZX Advent.
At first, after experiencing (but most likely not completely comprehending) the story, I thought that Ciel made Model XZHFLP, whilst I thought that (at first) it was Dr. Viel who made Model V. Then, after playing ZX Advent, I learned that Albert created(?) Model V.
And I need some clearing up. While Aile/Vent were away, they left Models HFLP in a lab, and someone stole 'em? Also, why was Aile/Vent compatible with HFLP?