So, why "Standing at Zero"? You know the numbers across the front of the stage? Zero is center, and we are putting one performer front and center.At the end of April, this month's honoree opened in his second Broadway show, Tootsie. His previous outing was of the feline kind. In the recent revival of Cats, he understudied both Munkustrap and The Rum Tum Tugger. Before that, Harris Milgrim toured the country as a J…