Can you clarify what generation RS forks you are referring to? Older Lyriks that had a travel range of 150 to 170 or the latest 2023/2024 Lyrik that has a travel range of 140 to 160mm.
Note too that the previous generation has a 42mm offset versus the latest generation is 44mm (Yes, I know there is a 51mm version offset too.)
The Zeb is a heavier duty fork having 36mm tubes versus Lyrik's 35mm. Plus a weight increase of over 200 grams for the Zeb. Reviews and posted comments are all over the place regarding which fork performs better. Most comment that it depends on the rider's weight and the types of terrain you ride on.
I just double checked, the difference between this generation and the last generation is not much and the 64.5 degree head angle is with a 572 fork.
- The new 160mm Lyrik is about 571
- My 170mm Lyrik is 581
- The new 160mm Zeb 576
I would recommend overforking, especially if the bike is on the bigger side for you. If you can get a 170mm Lyrik, I love mine and I only wish for a Zeb when doing a lot of downhill.
My 170mm Lyrik is 581 long puts my large frame at 64.1 degree head angle and it climbs well. Definitely could be more slack before I lose pedal efficiency.