Normally they couldn't be merged. You could of course try it with quite complicated expressions (nested if- and aggr-constructions with totals and some set analysis) to force the dimension and expression to show your results. But this could be very expenses and if it worked the performance could be rather slow.
Therefore are there other options? Like changes within the datamodel or to show two or more objects parallel at the same time within a conatiner in grid-mode or ...
