New version for huge directory: https://gist.github.com/kenoss/85ed24b3d168234a16d5f4f7a1e0b29a

peco-find-file-for-huge-directory.zsh

function peco-find-file() {
    local command
    if git rev-parse 2> /dev/null; then
        command='git ls-files'
    else
        command='find . -type f'
    fi
    local selected_files=$(eval $command | peco --prompt "[find file]")

    LBUFFER="${LBUFFER% } $(echo ${selected_files} | tr '\n' ' ')"
    zle redisplay
}
zle -N peco-find-file
bindkey '^u^f' peco-find-file