In many respects, Zimmer had a terrific year: The university won the Obama presidential library sweepstakes, for example, and U. of C. Medicine announced that it would open a badly needed Level I trauma care center, a move applauded by virtually the entire South Side. Numbers, however, may be catching up to this trained mathematician. The many ambitious projects he has launched during his nine-year tenure have been costly, prompting whispers that a restructuring and layoffs may be on the way.