Let X,Y,Z$X,Y,Z$ be random variables jointly distributed on the same probability space then we know the conditional probability $P(X=a,Y=b|Z)$$P(X=a,Y=b\mid Z)$ is a random variable which is $Z$ measurable. Can we say
$$P(X=a,Y=b|Z)=P(X=a|Y=b,Z)P(Y=b|Z)?$$$$P(X=a,Y=b\mid Z)=P(X=a\mid Y=b,Z)P(Y=b\mid Z)?$$
Moreover is it true to say
$$E[P(x=a,Y=b |Z)]=P(x=a,Y=b)?$$$$\operatorname E[P(x=a,Y=b \mid Z)]=P(x=a,Y=b)?$$