Zeb vs Lyrik for Lighter Rider

I've got both, if you like riding rough stuff fast ZEB is far superior due to the chassis stiffness.
If you like smooth flow/jump trails might not make as much a difference.

The added stiffness is always a benefit when cornering or holding a line in the chunk.

I would also suggest that riding style and where you plan to ride should factor into this decision more than just your weight. If you ride bike parks a lot, or like ARider said, ride a lot of rough at high speed, you might benefit from the ZEB. As to your riding style, if you ride rough terrain very aggressively, hitting every drop and rocky line you can as fast as you can, ZEB might be beneficial. If you're more of a careful line-choice guy who maybe isn't quite so aggressive, the Lyrik might be a better choice, especially at your weight. There's a pretty good weight penalty so you might want to think carefully about it.

So as a rider on the lighter side myself I think the larger air forks actually have a little unthought of benefit. The lyrik was always a bit more progressive than I’d wanted, not horrible but wish I had a little more room to play with. The extra volume in the Larger (Zeb/38) lowers and larger air chambers allow for a little wider tuning range which works well for lighter riders. Also the Zeb vs Lyrik in stiffness if you have a ad up on it is not overly stiff and only improved in torsional I believe so that it doesn’t pick up any extra harshness.

If weight isnt a huge concern I don’t see why I wouldn’t do Zeb/38 at 170mm