There's nothing wrong with the zone blocking scheme itself, it's the lack of evolution of around it that is the primary issue for Iowa IMO. Iowa finally added the jet sweep to the inside zone to give teams something to think about this year; and that was something Wisconsin and others have been doing since ~2010. Iowa has always run pin & pull outside zone but it's really the only consistent variation they use. Iowa really doesn't run
split zone looks much either, which is basically has a counter feel to it. Iowa will occasionally run "FB Sugar" zone looks, where the FB in I Form will go away from the play side but it looks very much the same to the front four, allows them to flow to QB pivot side at the snap.
All Xs and Os discussion aside they haven't had a skilled, load carrying back since Jewel Hampton left in '10. Coker was a reasonable fit in '10-'11, but didn't have ability to change direction at speed and struggled against good defenses. If you're going to run a mostly plain-jane zone blocking scheme, you better have a Shonn Green or Jewell Hampton type back who can create YAC on their own and make teams pay for over-pursuing. Iowa simply hasn't had one on the roster in awhile and is trying to run the same scheme; not a recipe for success in the ground game.