It isn't as much of a problem with PZI as it is with Lantus or Levemir, but shooting early creates overlap and overlap, if it is strong enough, can cause unanticipated lows.
However, with PZI, you could slightly reduce your dose to compensate for that, so I might take the dose, figure out what number of hours early it would be - if a quarter of the 12 hours, I might drop the dose a quarter.