Are you prescribed
Zantac? Or, are you talking about the OTC preparation?
Zantac is a very safe medication, it probably wouldn't be an issue for you to try it...run it by your doc first.
These meds can cause all kinds of GI Upset, so it could very well be the Prozac. Have you ever been diagnosed with GERD? Have you ever just tried taking a few Tums? That may work also. Tums can be very effective, and they are completely safe.
Make sure you are taking the Prozac as prescribed.