What is the language generated by this grammar:
G=({S,X,Y,Z,A,B}, {a,b,u,v}, P, S)
S -> XYZ
X -> AXA | BXB | Z | E
Y -> AYB | BYA | Z | E
A -> a
B -> b
Z -> Zu | Zv | E


I have not found
I think is 2 b's more than a ou 2 a's more than b. But u and v ?