You missed an easier alternative that was in the article: ctrl-u saves and clears the current line, then you can input new commands, then use ctrl-y to yank the saved command.
With zsh, I prefer to use alt-q which does this automatically (store the current line, display a new prompt, then, after the new command is sent, restore the stored line). It can also stack the paused commands, e.g.:
$ cp foo/bar dest/ <alt-q>
$ wcurl -o foo/bar "$URL" <alt-q>
$ mkdir foo <enter> <enter> <enter>
When you're killing (C-u, C-k, C-w, etc) + yanking (C-y), you can also use yank-pop (bound to M-y in bash and zsh by default) to replace the thing you just yanked with the thing you had killed before it.