Vim has a "smartcase" feature, which makes searching case insensitive, but only if the search contains all lowercase letters. When you search on any uppercase letters, smartcase assumes you want a case sensitive search. Is there a way to get the same behavior in zsh's tab completion?
Take a look at my zshrc file.
https://github.com/martincanaval/arch-conf/tree/master/etc/zsh
I have that functionality you are asking for and I believe this line made it.
zstyle ':completion:*' matcher-list 'm:{a-z}={A-Z}'