The Royal House of the Northern Tribes were becoming more powerful, but they were still a distance away from catching up with the Great Qin Empire.
The Great Zhou Empire managed to retain the last of their strength because of the Celestial Sect of Wonders' mercy. However, the Great Zhou Empire's might plummeted right into the abyss.
The Great Qin Empire sustained heavy losses during the War of the Two Worlds, and that wasn't even enough to describe their predicament. They were in a precarious situation for a while, but they managed to stabilize themselves.
Even though they also suffered a decline in strength, they had an advantage over the Great Zhou Empire.
The Great Qin Empire wouldn't have any advantage at all if the Royal House of the Northern Tribes and the Great Zhou Empire formed an alliance.