They received that as a gift from one of his friends. He (gifter) has a good video showing how it all went down and started with the premise of what to buy your friend when he's getting married when he "has everything he wants/needs". They are an awesome couple doing some awesome things (he even built a lift [elevator] from their living room up to their master bedroom in the house, and it's pretty cool!!), and also have some awesome friends.
The first version that he built, using two Rad Rovers was pretty cool and I'm sure myself and others would have been happy with that, but he went on to make a custom frame version that was even better. They've even gifted one to a fortunate disabled recipient. Now they're turning it into a business as I'm sure there are many out there that could benefit from such a machine. And if I ever see one on the trails, awesome!! They're definitely part of the e-group!!
What I remember is that Zack started a crowd funding campaign on his channel and he also pitched in along with Dan (the guy who started the whole thing) and thousands of others; all in all, they were able to raise enough funds to build a school. I that was super cool and very generous.