HIST_IGNORE_ALL_DUPS will throw out all previous matches of the command, which can be confusing when using the history as a log of what you did later:
If a new command line being added to the history list duplicates an older one, the older command is removed from the list (even if it is not the previous event).
A closer fit to your needs is probably the
When searching for history entries in the line editor, do not display duplicates of a line previously found, even if the duplicates are not contiguous.
Or maybe the
HIST_IGNORE_DUPS, but, as RichieHH notes, it also leads to an incomplete account of history:
Do not enter command lines into the history list if they are duplicates of the previous event.
man zshoptions | less -p History.
I can’t see any way to literally only do that, but if you set the
HIST_IGNORE_ALL_DUPS option, only the most recent version of a command will be retained in history, giving you the same effect.
man zshoptions for details.