All these files should be sourced, not executed; and Debian's lintian complains:
W: zsh-syntax-highlighting: script-not-executable usr/share/zsh-syntax-highlighting/zsh-syntax-highlighting.zsh
Fixeszsh-users/zsh-syntax-highlighting#188 in the case that both the
opening '((' and closing '))' have been typed, The case that only the
opening '((' have been typed is also fixed, but requires a zsh development
build (zsh-5.1.1-52-g4bed2cf or newer); see comments within.
* Don't override user defined styles
* Better modularisation of highlighters
* Allow to define which highlighters are activated
* Allow to define the order in which they are defined
* Minor performance optimizations
* Fixed some variables leak
* Improve documentation
* Brackets highlighter: use ZSH_HIGHLIGHT_STYLES instead of a specific array