I'd say E - both (1) and (2) are not sufficient to conclude that xyz > 0 because:
For xyz > 0, either x,y,z > 0 or any two are < 0 and the third > 0
(1) says xy > 0 but says nothing about z - so its not sufficient by itself
(2) says yz > 0 but again says nothing about x - so its not sufficient by itself
Therefore, answer is either C or E.
If xy > 0 either x and y are both > 0 or x and y are both < 0.
x and y are both > 0
Then z is also > 0 (since yz > 0 from (2))
And xyz will be > 0
x and y are both < 0
Then z must be < 0 (since yz > 0 from (2)
And xyz will be < 0
Hence (1) and (2) together are not sufficient.
Therefore answer = E
Help me crack the GMAT .. !!