/lib/x86_64-linux-gnu/libz.so.1 is in zlib1g 1:1.2.8.dfsg-2+b1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /lib/x86_64-linux-gnu/libz.so.1.2.8
/lib/x86_64-linux-gnu/libz.so.1.2.8