Taoist Xuanmen and Buddhist Buddhism, when combined together, do they constitute Xuankong?

It can be said literally.

However, Xuan Kong is a Yi Xue word. The chapter "On Xuan Kong" in "Shen's Xuan Kong Xue" explains the meaning of Xuan Kong as follows: "The word Xuan Kong means "ran" from one to nine. One to nine are not definite numbers, and there are intricate insights and understandings between them. Therefore, it is replaced by the word Xuan Kong. "The meaning is: Xuan Kong represents the numbers 1 to 9. Because 1 to 9 are not arranged according to the prescribed order, but have many variations, so Xuan Kong is used instead. Xuan Kong is mainly used in geographical Feng Shui, so there is a school of geographical Feng Shui called Xuan Kong Feng Shui.

And together they often talk about Buddhism and Taoism.