How to find location of installed library

Easy! dpkg -L packagename. That will list all files (with location) that were brought in by the package.

In case if you are not sure about package name you could list all packages and try to find requested:

 dpkg --get-selections | grep -v deinstall | grep <packagename>

 For example:
      $dpkg --get-selections | grep -v deinstall | grep zip
 Output:
      bzip2                      install
      gzipinstall
      p7zip-fullinstall
      unzipinstall                                                                       
      zipinstall                         
  And then:
      $ dpkg -L zip
  Output:
      /.  
      /usr
      /usr/share
      /usr/share/doc
      /usr/share/doc/zip
      /usr/share/doc/zip/copyright
      /usr/share/doc/zip/TODO
      /usr/share/doc/zip/changelog.Debian.gz
      /usr/share/doc/zip/WHATSNEW
      /usr/share/man
      /usr/share/man/man1
      /usr/share/man/man1/zipsplit.1.gz
      /usr/share/man/man1/zipcloak.1.gz
      /usr/share/man/man1/zip.1.gz
      /usr/share/man/man1/zipnote.1.gz
      /usr/bin
      /usr/bin/zipsplit
      /usr/bin/zipcloak
      /usr/bin/zip
      /usr/bin/zipnote
      /usr/share/doc/zip/changelog.gz