I recently switched to zsh, so I changed my .screenrc to reflect that
(shell zsh). Now, when using zsh inside screen, the key sequence
CONTROL-K, which usually deletes a line, a-la emacs, produces the
literal string '^K' on the command line.

Oddly, some other sequences, like CONTROL-W produce the expected
outcome.

Any clue why this might be?

Thx, Kyle