Orchestrating Observable: make parallel network calls, then combine the result into a single data point (using flatmap & zip)

The below ascii diagram expresses the intention of our next example with panache. f1,f2,f3,f4,f5 are essentially network calls that when made, give back a result that's needed for a future calculation.

         (flatmap)
f1 ___________________ f3 _______
         (flatmap)               |    (zip)
f2 ___________________ f4 _______| ___________  final output
        \                        |
         \____________ f5 _______|

The code for this example has already been written by one Mr.skehlet in the interwebs. Head over tothe gistfor the code. It's written in pure Java (6) so it's pretty comprehensible if you've understood the previous examples. I'll flush it out here again when time permits or I've run out of other compelling examples.