"This snow lets me know I'm getting old," Zimmerman, 44, said later in the morning as he rammed his truck over and over into a snowdrift that had trapped a bus. "When I was young, this was fun."
School bus contractors across Maryland are in the same predicament, working to get buses ready for when schools reopen.
As state and county crews clear roads and residents shovel their cars out from under mounds of snow, thousands of school buses remain stranded in their parking lots.
He started the work early Monday, before the snow stopped falling, and kept at it for 16 hours. By 10 o'clock that night, when he called it quits, he had liberated half the fleet.
Never mind that he was bruised from getting jostled inside the cab of his snow loader, another piece of machinery that has proved invaluable this week. Schools will reopen eventually, and he wants to be ready.
Zimmerman estimates that by the end of the week he will have freed 60 school buses - including some that belong to fellow contractors who don't have snow-clearing machinery - and plowed several acres of parking lot.
With little choice about where to pile the vast amount of snow, Zimmerman's work was slow-going.
When he had cleared an area in front of a vehicle, he or an assistant would rev up the bus engine, and the vehicle would shoot forward, clearing the bed of snow on which it had been parked.
Zimmerman's drivers are starting to feel cooped up in their homes and are eager to get back to work, he said. In these driving conditions, with streets made narrow by piles of snow and slick by ice, he constantly reminds his crew: "Go out there and drive like you've got sense."
That could be why his drivers haven't been in an accident in the past six years while shuttling schoolchildren around the county.
Shawn Cousins, who has worked for Zimmerman for eight years, said yesterday that she misses her students but didin't think she could handle her northern Anne Arundel County routes yet.
"Some of these mounds are so high, I wouldn't be able to find my kindergartners," she said.
Yesterday afternoon, Zimmerman interrupted his work briefly to bail out another of his drivers, who shuttles airport employees daily between downtown Baltimore and Baltimore-Washington International Airport. The woman's minivan was stuck at the far end of a narrow, unplowed residential street in Brooklyn Park.
On the way back to his lot, Zimmerman stopped to chat with another bus contractor, whose property he helped clear in the morning. He learned that Anne Arundel officials had decided to keep schools closed for the two next days.
He heaved a sigh of contentment. "Now I can go back and drink a beer and call it a day," he joked. Then he added that he would probably use the extra time to shovel out the homes of his mother and sister, who have been unable get out.