Strange Construction

"The Seller undertakes to replace defective goods free of charge within the minimum possible time, the Agent to pay the cost of transportation and insurance."

What is name of the construction that I've written with black type? I have never seen such constructions before.

It's omitting the verb "undertakes" which carries over from the beginning of the sentence.

Thanks. I think I've realized the meaning of the sentence but does it sound natural?

It's not supposed to sound natural -- a lawyer wrote it. ;-)