It was ironic that life force could be used to summon the Army of Anubis when life and death were opposing powers. Yet, it was life force Zheng used to summon several Anubis Warriors.
Infinitesimal control allowed Zheng to utilize energy in minor amounts instead of letting the Bracelet of Anubis drain all his energy like it used to. Once the life force of the Ents entered his body, he summoned several warriors as expected. Gandalf and the Ents frowned upon seeing these monsters with the head of a dog and bodies of men.
Despite believing these monsters were from evil summons, Gandalf and the Ents agreed to Zheng due to the pressure of the hundreds of thousands of the Mordor army. The Ents would focus their energy to Zheng and had him summon the Army of Anubis.