Rushing defense and RZ defense aren't really related to each other, as evidenced by the Lions. Otherwise they wouldn't be 2nd in one category and 27th in the other.
A team like the Lions were stout against the run and still ended up 27th in RZ defense. Is it because their opponents scored a lot of RZ TDs thru the air? Seems like a good strategy to me: Why try to run against the #2 run defense in the RZ when their pass defense is #29?
On a related note, I did a little research for a post I wrote on November 21 and it seems relevant here:
The Rams had 10 touchdown runs thru 10 games. They have covered 1 yd, 7 yds, 1 yd, 4 yds, 3 yds, 3 yds, 5 yds, 1 yd, 1yd, and 1 yd.
Every single rushing touchdown the Rams scored in their first 10 games was a red zone run. I didn't check the final 7 games, but the Rams' RZ rushing attack seemed to be on track at least thru the first 10 games.
AlbaNY_Ram