The Walkera Voyager 4 has a 18x optical zoom, but it's not competing with the Phantoms. Not at a price at around $4700 US. That's competing with the Inspire and Zenmuse cameras. While they don't have an 18x zoom, you have a choice of lens and a much better sensor.
You also have to know that "18x" doesn't mean "super zoom". It just means that the maximum focal length is more or less 18 times the minimum focal length. Which for the Voyager 4, means 6.7mm to 134mm. It uses a 1/2.3" Sony sensor, much smaller than the 1" sensor in a
Phantom 4 Pro or the Micro 4/3 from the Zenmuse. With a tiny sensor, that lens will seem like a large zoom, but it will be noisier than the Phantom sensors.