Let's take a sum and an example production
$z_{1}=\sum_{k=1}^{3}(k!+(k+1)!)$
and
$z_{2}=\prod_{k=1}^{3}(k!+(k+1)!)$
I wish to get in z1
a result like that
$z_{1} =(1! +(1+1)!)+ (2!+(2+1)!)+(3!+(3+1)!)$
likewise for z2
such a result
$z_{2} =(1! +(1+1)!)(2!+(2+1)!)(3!+(3+1)!)$
I used different variations of Hold
but could not come up with anything
help me a little.