As a private attorney, John Z. Lee would submit a motion and then start to wonder after a couple of weeks what was taking the judge so long to issue a ruling.He learned the reason after becoming a judge himself 6½ years ago.“What I did not appreciate when I was a lawyer was just how full the docket is and just how challenging it is to keep cases moving in a way that is fair to all the parties involved,” Lee said.But the challenges of serving on the federal trial bench in Chicago have not discouraged Lee …