It can be very confusing who has right of way when merging but it is simple if we think about whether there’s line markings or not. If no lines then it’s a Zip Merge, if there are lines then it’s a Lane Change.

When there’s no line markings it’s a Zip Merge, then it’s the vehicle in front that has right of way. The red car in the diagram below must give way to the green car.

When there’s line markings it’s a Lane Change, therefor you must give way to the cars in the lane you are changing into. The red car in the diagram below must give way to the green car.