Download package from: https://download.zerotier.com/dist/qnap/
zerotier_1.10.1_x86_64.qpkg
Use WinSCP to move the file onto the NAS
Install QVPN from the APP Center within QNAP
SSH into the nas to the directory where you put the file with WinSCP
install it with this command: sudo sh ./zerotier_1.10.1x86_64.qpkg
Type the below commands line by line
cd /share/CACHEDEV1_DATA/.qpkg
ln -s 0Tier1 ZeroTier
ln -s 0Tier1 zerotier
cd ZeroTier
ln -s usr/sbin/zerotier-one
cd /usr/sbin
ln -s /share/CACHEDEV1_DATA/.qpkg/ZeroTier/zerotier-one
cd /var/lib
ln -s /share/CACHEDEV1_DATA/.qpkg/ZeroTier zerotier-one
/share/CACHEDEV1_DATA/.qpkg/ZeroTier/0Tier1.sh start
NOW zerotier-cli should work!