This is hard... I would need more examples to be sure of my pattern, but here is what I got for the first one.
The first letter is associated to the number of loops in the cloud.
6 = F, 5 = I, 4 = H and 3 = G
The Second letter depends on the most important circle inside.
If there is a greyed out circle, X, else if there is a black circle, Z, if only white circles, V.
Here is what I got for the second one.
The first letter is the state of the biggest square. E = Cross, F = Full, H = Half, G = Grid
The second letter is the position of the small square. Up left = L, Up Right = M, Down left = G, Down right = N
Do I sound stupid? Somehow it seems to make sense to me...