My experience with myself and children is the Zpaks are hard to handle for alot of kids.
My kids get diarreah. I always stop and now won't return due to stomach ache on day 2.
I have found calling the doctor in the a.m., reporting this common issue of upset stomach, they will gladly allow you to come in, get a shot.
A few seconds of pain, immediate relief within 12 hours. My kids ASK for shots now when told they need antibiotics.
Bribe them with Milkshakes afterwards, they will thank you for the 4 seconds of pain that ends in health and pleasure.