You make some good points and I'll take them under advisement. But yes, they are brains, and a popular idea in zombie mythology is that their brains swell as they zombify, hence the bulging. And yeah, I had a feeling that the mouth and moustache were too close to each other, thanks for the feedback.
If those are brains, it's strange that they are bulging OUT of the zombie's head, even casting a shadow. It looks like a pink leaf sitting on top of his head. Also, I know the moustache is supposed to look fake, but it would be easier to differentiate between the mouth and the moustache if they weren't both so similar in color. The are both very orange. Maybe try making the moustache darker?
Ah, okay about the brains. That actually makes even more gross! :D