I wish tabs would have separate (non-shared) history. I did try this [0] but it doesn't work all the time (!?).
0: http://apple.stackexchange.com/questions/75571/the-history-i...
0: http://apple.stackexchange.com/questions/75571/the-history-i...
Edit: I wrote a thing here about the difficulty of carrying history across terminal sessions and how can you associate a tab you open now with a tab you had open in a previous session, but then I realised that I misread your post.
I would expect the answer in the posted link to work. The 'share_history' option, when set, tells zsh to reread the history file before performing history lookups.
Maybe try the set-local-history option documented here?
1: http://zsh.sourceforge.net/Doc/Release/Zsh-Line-Editor.html#...