✓ Mathematica : cpu = 0.009907 (sec), leaf count = 29
DSolve[6*x*Derivative[2][y][x] + 6*x^2*Derivative[3][y][x] + x^3*Derivative[4][y][x] == 0,y[x],x]
✓ Maple : cpu = 0.012 (sec), leaf count = 18
dsolve(x^3*diff(diff(diff(diff(y(x),x),x),x),x)+6*x^2*diff(diff(diff(y(x),x),x),x)+6*x*diff(diff(y(x),x),x)=0,y(x))