/usr/share/zsh/functions/Completion/Cygwin/ is in zsh-common 5.1.1-1ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/share/zsh/functions/Completion/Cygwin/_cygcheck
/usr/share/zsh/functions/Completion/Cygwin/_cygpath
/usr/share/zsh/functions/Completion/Cygwin/_cygrunsrv
/usr/share/zsh/functions/Completion/Cygwin/_cygserver
/usr/share/zsh/functions/Completion/Cygwin/_cygstart
/usr/share/zsh/functions/Completion/Cygwin/_dumper
/usr/share/zsh/functions/Completion/Cygwin/_getclip
/usr/share/zsh/functions/Completion/Cygwin/_mkshortcut
/usr/share/zsh/functions/Completion/Cygwin/_mkzsh
/usr/share/zsh/functions/Completion/Cygwin/_pscp
/usr/share/zsh/functions/Completion/Cygwin/_putclip
/usr/share/zsh/functions/Completion/Cygwin/_readshortcut