For those who are also into classical astrology like me, you will know that bazi actually models after it. It is interesting to note that the 5 elements in the diagram above refer to the planet(s) governing each horoscope.
Capricorn and Aquarius are governed by Saturn. In ba zi lingo, it implies the rat and ox palaces are governed by earth star. Hence, under the 6 combo, you have rat and ox combining to give earth element. Whether they combine and really transform is another thing.
Having some insights of classical astrology will definitely open up and give you better perspectives when learning ba zi including what the 4 pillars imply from the angle of astrology.
One of the classics, Xing Ping Hui Hai 星平会海, examines this.
I look forward to sharing more with the class this weekend.