I don’t believe Hillary and Zack are in the same room. I doubt Hillary saw any of Zack’s lines. I think she just read some lines into a camera, (probably including many we didn’t see) and they spliced it together.
It really does feel that way, doesn’t it? There is absolutely zero human interaction between them. No back and forth, no repartee. It takes incredible talent for actors to play their roles in front of green screens —talent not available in Clinton at all.