Zeus used the Youth Holy Grail, the companion Divine Artifact of the Youth Goddess Hebe, to restore his physical energy. In fact, Nezha had long noticed a weakness of the Greek Gods—their Divine Power came from the blessing of the world's origin. Their omnipotence was due to the support of Divine Power.
However, using Divine Power came with a cost: their physical energy. In other words, they had a physical energy bar. When the energy bar was emptied, their combat ability would plummet drastically, and this was no exception even for God King Zeus.
Though his energy bar might outlast the lives of many other gods, it had its limits. His method of replenishment was to plunder the Divine Artifact—the Youth Holy Grail—belonging to his own daughter.
Nezha discovered this when interacting with Hebe earlier, so he had always guarded against this vile Zeus replenishing his energy. This strike had been meticulously prepared for a long time.
