First of all Ancient Zoan or not, once he gets cut it is over. You ignored the breath of all things, which would allow Zoro to cut anything and nothing. I didn't even mention Zoro's aura, which could likely just make P1 show his belly.
Also, Denjiro smirked, but he was not smirking the whole time. Everytime Zoro attacked he had a different face on. Also, Pica and Vergo had full body haki, Zoro cut that like butter.
Yes Zoro told him to move but Zoro was not after Kyoshiro, he went after Orochi. Then Kyoshiro explained he was orochi's dog and they stopped fighting.