DNA molecule splits and recombine when cell division happens as long as the zipper when you zip the two strand are intact to one another and when you unzip it they separate into two. In general the DNA recombination and spliting can make a replication for itself while the zipper can separate from another strand that can make also another of itself.

DNA molecule is comparable with a zipper because when bases in each strand are bonded to each other it looks like a closed zipper but when separation takes place it seems like a zipper that is opened slowly as the bases separates just like the tooth of the zipper separated from its pair from the other side