You sure?
Cause ZSS nair does exactly 10% in training mode, as well as in versus mode...
Nope, not sure at all!
That's why I'm asking. A long time ago, FadedImage (one of the earliest ZSS mains around in SoCal) explained to me that in training mode all moves deal 105% damage, and I just took that at face value.
To be honest I've had codes that allow stale move negation in training mode for so long that it's not really relevant to me anyway :\
EDIT: Also I just read about ZSS' recovery in the discussion above, and I think Infinite guy has this right. ZSS' recovery has to be played against pretty carefully because of the threat of down b (both the kick and headbounce versions -- one offers a spike, the other offers safety if the opponent doesn't account for it) but it isn't really used much because if the guy is just standing there onstage in a neutral state it's very easy to punish it.
In other words, the down b provides an option that has to be accounted for, and that's about it. I think her best recovery tool is probably the boost jump from up+b to be honest. In addition ZSS has a lot of aggressive options for punishing guys who try to edgehog or gimp her aside from down b (like her uair if coming from below etc.)
ZSS' recovery isn't the best in the game and generally speaking she takes some damage off-stage but she usually makes it back, too. It's really hard to stop her from coming back to the stage. Note that this doesn't mean it never happens, she uses tethers after all.