I have my basset hound mix a sweater for when it gets really chilly her as she has to be walked at least once a day to burn out her energy and keep her happy.

A sweater is good, and so are the booties, they aren't too expensive and trying them out one at a time inside first is a great idea. That way Zepplin can adjust to them and if he absolutely hates them save the recipit and take them back to whereever you bought them for a refund. That is what I did with the sweater with my dog Scout in case she didn't like it. After a few try ons with the sweater she didn't mind anymore

Booties are ideal since dogs release heat through the pads of their feet, but a sweater will also help trap and maintain body temperature on their body as well.