I will be moving shot time in increments of 15 minutes. This is how Lantus needs to be done but since PZI is much more flexible, you may be able to do half an hour. If it's easier for you to shoot early, then you could start moving the shot before Sunday. If it's easier for you to shoot late, move it after.
So if your shot time is 9:00, and you want to do it in 15 minute increments, Wednesday you would shoot at 8:45, Thursday at 8:30, Friday at 8:15, and Saturday at 8:00. Then Sunday when you wake up, 8:00 will be 9:00 and you are back on schedule.
In reverse, you would shoot on Sunday at 10:00 ( the old 9:00) and move to 9:45 Monday, 9:30 Tuesday, etc.