Zhenzhen taught how to use your Qi to heal yourself to Xiong Delun and Xiong Delun taught this to his brothers and also use his Qi to heal others.
During their testing, using Qi to recover their health and stamina after exhaustion, they found out that Xiong Qiang has the most suitable Qi to recover health and stamina at a very high speed.
And given that Xiong Qiang has a black dragon inside him who has an unlimited amount of Qi and he can provide his Qi to Xiong Qiang,
Xiong Qiang is the best person to heal someone.
But there is one problem in this and that is, The more Xiong Qiang uses Black Dragons Qi as his own, the more corrupt his nature becomes and the results are him being too aggressive and blood thirsty during battles.
Thus, Xiong Bo has to complete the task at a very high speed and not put his little brother under pressure, and before beginning this whole thing he told Xiong Qiang what he is going to do.