Zayn didn't count the days because they passed way too quickly.
He hunted various monsters and manifested the Spirit of those he deemed as the strongest. As for the remaining monsters, their Soul Wisps were allowed to ascend and disperse after the attached ownerless soul particles had been devoured.
Their corpses were devoured and turned into Soul Orbs which Zayn absorbed to increase his strength.
Slowly but steadily, Zany was getting stronger and the register of his Spirits increased rapidly.
His small unit consisting of five Winged Serpent Spirits expanded a bit. Their numbers doubled in size!
At first, Zayn was pretty sure that five Winged Serpent Spirits were enough. However, he recalled that Spirits could be fused and that a higher compatibility between the Spirits would result in a much higher success rate of a Soul Fusion. That way, he wanted to create a Winged Serpent with much higher talent once he learned the Soul Fusion technique.