The four pillars are used to calculate the blessings and misfortunes of a person's life, and the six lines are very useful in calculating sudden events. The Four Pillars and Six Yao are multi-dimensional unity.
Six Yao is simple, easy to learn but difficult to master. It is a common method. The theory of Six Yao is found in the Four Pillars, Feng Shui and Physiognomy.
The Four Pillars are complicated. To learn the Four Pillars well, it is best to learn the Six Yao first.