/usr/lib/x86_64-linux-gnu/libzmq.so is in libzmq3-dev 4.1.4-7.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libzmq.so.5.0.0
/usr/lib/x86_64-linux-gnu/libzmq.so.5.0.0