Quoting Message-ID: 
<237967ef0801040304h494987bv939bf6ff9541123f@mail.gmail.com> from zsh-user-ML:

#######################################################################
And I have this custom widget to help me store a command line in history
without executing it:

   commit-to-history() {
      print -s ${(z)BUFFER}
      zle send-break
   }
   zle -N commit-to-history
   bindkey "^X^H" commit-to-history

So, I type a command, hit Ctrl-X Ctrl-H, and then retrieve my command
from history when I need it.
#######################################################################

What do you think about that?