One of my side characters is a scientist, and he is zombie immune. This lets him get close enough to study the zombies. However, I feel like just saying he is a "biologist" might be too broad. A lot professional scientists are specialized in something, right? Perhaps some sort of human anatomy or disease specialist would be ideal to make him the best guy for the job? Or is just "biologist" good enough?.
I'm aware the absolute best option might vary slightly depending on the specific traits of the zombies, but for stereotypical zombies surely there is a short list of specialties, probably mostly in the field of biology, that would make a person uniquely qualified for trying to study them?