Firstly, not simultaneous. Secondly, Battersea and Whitechapel are not the same geographical area.
Details, Fish, details...
Overlapping equals simultaneous. Nobody is suggesting that he killed all victims in the exact same minute.
We have no idea whether he picked up any of the victims in Battersea, by the way - if you can go from Whitechapel to Battersea, you can go from Battersea to Whitechapel. And double quick, too.
Details, Gareth, details - and facts!
Of course, your purpose will be to obfuscate. The sum of all matters will nevertheless be that we know of no obstacle at all preventing the two series to have been perpetrated by the same killer. Not a single one.