What is the parallel structure of this sentence? To install new carpeting, workers must first remove the old carpet, prepare the surface, and then lay down the matting

Answer 1

It looks parallel to me.

The series has 3 parallel verb phrases in it:
~ remove the old carpet
~ prepare the surface
~ lay down the matting

The only thing I would suggest is to move "then" to the second verb phrase and then include "finally" or "last" with the third verb phrase ... like this:

~ first remove the old carpet
~ then prepare the surface
~ finally lay down the matting