If installed via home-brew on OS X, the help needs to be set to a different path.
Installed zsh completions via home-brew, config adjusted as per install directives.

==> Downloading https://github.com/zsh-users/zsh-completions/archive/0.10.0.tar.gz
==> Caveats
To activate these completions, add the following to your .zshrc:

  fpath=(/usr/local/share/zsh-completions $fpath)

You may also need to force rebuild `zcompdump`:

  rm -f ~/.zcompdump; compinit

Additionally, if you receive "zsh compinit: insecure directories" warnings when attempting
to load these completions, you may need to run this:

  chmod go-w /usr/local/share
==> Summary
🍺  /usr/local/Cellar/zsh-completions/0.10.0: 100 files, 828K, built in 2 seconds
Changed configuration to enable syntax highlighting as per install instructions from homebrew

==> Downloading https://github.com/zsh-users/zsh-syntax-highlighting/archive/0.2.0.tar.gz
Already downloaded: /Library/Caches/Homebrew/zsh-syntax-highlighting-0.2.0.tar.gz
==> Caveats
To activate the syntax highlighting, add the following at the end of your .zshrc:

  source /usr/local/share/zsh-syntax-highlighting/zsh-syntax-highlighting.zsh

You will also need to force reload of your .zshrc:

  source ~/.zshrc

Additionally, if your receive "highlighters directory not found" error message,
you may need to add the following to your .zshenv:

  export ZSH_HIGHLIGHT_HIGHLIGHTERS_DIR=/usr/local/share/zsh-syntax-highlighting/highlighters
==> Summary
🍺  /usr/local/Cellar/zsh-syntax-highlighting/0.2.0: 33 files, 160K, built in 2 seconds
Forgot the conditional part of the "If OS X ..." of the last three commits.