just in case you want to mess around with that
there is a "zerotier_broadwellnk-6.2_1.4.0.spk" and that "broadwellnk" is a x64 dsm 6.2.x system the same as 3615/17 and 918+ are, the package seem not to contains a driver that would be bound to a kernel, it looks like a normal software and if its for 6.2 and x64 it should run on all x64 versions
when replacing the file "INFO" inside the package with one that contains
arch="x86_64" instead of the arch="broadwellnk" the it would install an all the tree dsm's we have
the installer of the package references to tun.ko and that driver is part of the normal drivers dsm comes with (there is no *.ko file in that installer,so no danger of overwriting a kernel file you might need)