You have a lane that becomes a dedicated turning lane and another that continues straight. In that case it's on the cars in the lane that is turning to find a spot in the straight lane if they don't want to turn. A true zipper merge situation is where two lanes become one (either by design or in the case of a lane closure because of construction).

With all that said, the cars in the lane going straight should allow the cars to merge in when their lane is about to become a turning lane and not be punks about it, but there's no clear "zipper merge" spot in that situation. It's just another lane change.