It's not clear to me if it's different than Zerotier's routing design or not. Partly because ZT has their "moons" and custom network controllers. Googling about it does seem to indicate ZT doesn't support peers routing traffic directly, but you can setup your own DERP style TCP relays.

To me Tailscale is just a nicer version of Zerotier but not in different genre like ftp vs Dropbox. From a general non-power users perspective they operate almost identically.