Currently, Zsh’s extended_history option is not handled well in Emacs.
The comint buffer does not know to skip it when running
comint-read-input-ring. The attached patch handles this.

This behavior is described in the Zsh manual available at:

http://zsh.sourceforge.net/Doc/Release/Options.html#History

The format of this line looks like this:

: <beginning time>:<elapsed seconds>;<command>

This patch just skips those timestamp to get the <command> part.