The easiest (assuming what DMA said is true) would be to just buy a 120mm to 140mm transition piece (words fail me).
There's a couple here
... but one like this
would be better for airflow.
But it looks like it would have to be mounted on the ceiling/roof of the case, if it will even fit there (get out your tape).
If you are more concerned about function over form... mount it outside of the case at the back, cut a few holes for the tubing, or if the tubes are long enough, put them through an expansion slot (however, would require breaking the "seal" of the all-in-one).
Wait wait wait, it says that top fan is 200mm... so those mounting holes gotta be 140?... if not, drill...lol