This is the Belgian Tervuren, which someone suggested Zoe might be crossed with:

Belgian Tervuren are a lot bigger than Zoe: females 22-24″ and 60-70lbs. But look at the colors, especially the black-tipped fur and the black muzzle. Even the shape of the body reminds me of Zoe. So it’s definitely possible. Ironic, too - a herding breed.