Can I, a doctor, save 10 billion lives in another world?

Can I, a doctor, save 10 billion lives in another world? ManhwaI want to save all the lives in the world. With that sentiment, I worked as a doctor in a corrupt environment. Still, due to sudden death, I found myself reborn as a prince named “Eiji.” In a world w “religion” and “god” prevail, and no doctors could be found, witnessing the many lives lost due to these misguided beliefs, I used all of my knowledge from my previous life to perform surgeries and develop medical equipment.
Which is the one that saves lives: God or Medicine?
With the knowledge of 5000 years of medical history, both god and disease will be eradicated! Even if I have to go against god, I will save lives!