And, there's even a script that offers Fish-like syntax coloring for Zsh: https://github.com/zsh-users/zsh-syntax-highlighting/
But not having used Fish yet myself, I can't really offer any reasons to use Zsh over Fish.
Fish's consistent syntax for conditionals/loops is what brought me over in the first place, I always needed to work to remember what goes where in zsh/bash. For one-off tasks the reduction in mental overhead was a _huge_ win.
That said, I recently did switch back to zsh for a functional command-not-found handler - fish's only includes the name of the binary rather than the whole command, so I couldn't productively use it as a retry wrapper.
Bash script compatibility, bigger userbase and therefore more third party customizations.