Only if the current case is not matching, other cases are tried.
# Use a cache to speed up completions.
zstyle ':completion:*' use-cache on
zstyle ':completion:*' cache-path ~/.zsh/cache
-# Also match uppercase names when typed only lowercase.
-zstyle ':completion:*' matcher-list 'm:{a-z}={A-Z}'
+# Ignore the case if the currently typed string doesn't match.
+zstyle ':completion:*' matcher-list '' 'm:{a-zA-Z}={A-Za-z}'
# Enable zsh's extended glob abilities.
setopt extendedglob