Did you just start the game? I started around april 4th and wasn't able to get venti in his last day or tartaglia. I was able to hit pity of zhongli banner. But got dilic instead :( So it really depends if kazhuha is the first or second banner in 1.6. You may have a chance if its the second, but if its the first its not very likely.
Edit:Grind out ......
