Answer: The Book of Zohar is a commentary on the five books of the Torah and is divided according to the sections of the Torah. There are many parts of The Book including the preface.
The Torah describes the states of the upper spiritual worlds. The Book of Zohar describes the same thing, but in commentary closer to Kabbalists. It opens everything to a person.
The Torah is not intended to reveal the upper world to a person; it is simply a record of spiritual states. The Book of Zohar helps a person attain the upper world.
The Torah is a book that tells about all the depths of the management of our world, that is, the upper world, in all its details. And The Book of Zohar is a commentary, which explains what is written in the Torah but in an allegorical way. Therefore, only a Kabbalist can understand it.
But still it is closer to a person, and thanks to it we begin to realize what is said in the Torah itself.
“The Preface to The Book of Zohar” is a volume that describes the basic control system of our world. It is a collection of articles, each of which describes a certain control system, a specific node, a control unit, for our world. The Book of Zohar includes some other articles, such as “Idra Raba” and “Idra Zuta,” which express more internal depths of the system.
It is similar in our world. If we study some part of a car, the power system, for example. We study the carburetor, how it prepares the mixture for combustion in the engine, etc. That is, the work of a particular system is allocated in separate blocks. The same is true of the articles in The Book of Zohar: “Idra Raba,” Idra Zuta,” and “Safra de Tzniuta.”
From the Kabbalah Lesson in Russian 2/12/17