@sga:
You should install the ZeroTier package that is for your Enigma2 distribution. The package must contain ZeroTier, which has been compiled and therefore predestined, for a specific Linux kernel (dependency on software drivers and libraries).
Try installing ZeroTier from the feed server directly from your Enigma2:
# Enigma2 installation: opkg update opkg list | grep -i zerotier opkg install <enter_the_exact_name_of_the_installation_package_for_the_ZeroTier_client_here> reboot
If that doesn't help, then you need to find another package that will work specifically for your Enigma2 (I don't know which Enigma2 you use because you didn't mention it).