Specifically, is it possible to combine the products? Both summation/products carry the same bounds.
$$\sum_{n=2}^{x}\prod_{j=1}^{n-1}f(x,n,j)+\sum_{n=2}^{x}\prod_{j=1}^{n-1}f(x+2,n,j)$$
This is as far as I got:
$$\sum_{n=2}^{x}\left(\prod_{j=1}^{n-1}f(x,n,j)+\prod_{k=1}^{n-1}f(x+2,n,j)\right)$$
As already stated in a comment, there's no further simplification beyond what you've already done without more knowledge about $f$.