To save anyone doing the donkey work I viewed the comparison videos of the ZR1 and the GTR and here is the sections broke down into where the GTR loses time to the ZR1.
Yellow section ZR1 was ahead by 0.7s
Orange section ZR1 increased this to 1.3s
Plum section ZR1 improved this to 1.9s
Dark Orange Section ZR1 loses a whole second in the final turns at Adenauer Forst, dropping to 0.9s
Yellow Section #2 ZR1 improves again to 1.7s
Green section All high speed, ZR1 improves to 3.6s (most of this improvement is between Bergwerk and Klostertal)
Dark Orange section #2 The twistiest section on the track, GTR pulls back 1.5s dropping the gap to 2.1s
Light Blue section ZR1 gains another 0.5s to the finish, ending the lap 2.63s ahead.
At least now we can all discuss where each car is gaining and losing it's time.