There is research indicating that similar genetic factors can predispose a person to develop either of the conditions. But you can be diagnosed with schizophrenia or bipolar disorder based only on criteria from the “Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5).”
This is because one diagnosis will usually exclude the other. But if a person exhibits symptoms of both conditions but does not fit either of these diagnoses, they could have schizoaffective disorder.