✓ Mathematica : cpu = 0.324606 (sec), leaf count = 110
DSolve[nu^2*(4 + nu^2*x^2)*y[x] - 2*(6 + nu^2*x^2)*Derivative[2][y][x] + x^2*Derivative[4][y][x] == 0,y[x],x]
✓ Maple : cpu = 0.247 (sec), leaf count = 62
dsolve(x^2*diff(diff(diff(diff(y(x),x),x),x),x)-2*(nu^2*x^2+6)*diff(diff(y(x),x),x)+nu^2*(nu^2*x^2+4)*y(x)=0,y(x))