For me the ultimate trick is to open the current prompt in vim with F2 (Ctrl+X ctrl+E seems to work too):

  # Use F2 to edit the current command line:
  autoload -U edit-command-line
  zle -N edit-command-line
  bindkey '^[OQ' edit-command-line  # f2 is ^[OQ; to double check, run `xargs` and then press f2