Matrix t2*K(2) in Subspace 88 with Dimension 12

(K(2) is the second-order Grosse operator)

-3*t*U ((1 - I*Sqrt[3])*(4*t^2 - U^2))/4 0 0 ((3*I + Sqrt[3])*t*U)/(2*Sqrt[2]) -(((-3*I + Sqrt[3])*t^2)/Sqrt[2]) ((-3*I)*t*U)/Sqrt[2] 0 -(((-3*I + Sqrt[3])*t^2)/Sqrt[2]) ((-3*I + Sqrt[3])*t*U)/(2*Sqrt[2]) (Sqrt[3]*t*U)/2 0
((1 + I*Sqrt[3])*(4*t^2 - U^2))/4 (-15*t*U)/4 0 (((-3*I)/2)*t*U)/Sqrt[2] 0 Sqrt[3/2]*t*U 0 ((-3*I + Sqrt[3])*t*U)/2 -(Sqrt[3/2]*t*U)/2 0 (3*I + Sqrt[3])*t^2 ((-3*I)/4)*t*U
0 0 -5*t*U 0 ((I/2)*(5*I + Sqrt[3])*t*U)/Sqrt[2] 0 ((3 + I*Sqrt[3])*t*U)/(2*Sqrt[2]) 4*t^2 0 (t*(Sqrt[2]*U + (3*I)*Sqrt[6]*U))/4 0 0
0 (((3*I)/2)*t*U)/Sqrt[2] 0 -3*t*U -U^2/2 0 (-2 - (2*I)*Sqrt[3])*t^2 ((3 + I*Sqrt[3])*t*U)/(2*Sqrt[2]) (I/2)*Sqrt[3]*t*U (I/4)*(I + Sqrt[3])*U^2 0 -(t*U)/(2*Sqrt[2])
((-3*I + Sqrt[3])*t*U)/(2*Sqrt[2]) 0 ((-I/2)*(-5*I + Sqrt[3])*t*U)/Sqrt[2] -U^2/2 -4*t*U (1 - I*Sqrt[3])*t^2 (I/4)*(5*I + Sqrt[3])*t*U 0 ((4*I)*(I + Sqrt[3])*t^2 + (1 + I*Sqrt[3])*U^2)/4 (t*(U + (5*I)*Sqrt[3]*U))/4 0 (Sqrt[2] - I*Sqrt[6])*t^2
-(((3*I + Sqrt[3])*t^2)/Sqrt[2]) Sqrt[3/2]*t*U 0 0 (1 + I*Sqrt[3])*t^2 (-9*t*U)/2 (I/4)*(3*I + Sqrt[3])*U^2 ((1 - I*Sqrt[3])*t*U)/Sqrt[2] t*U (1 + I*Sqrt[3])*t^2 ((1 + I*Sqrt[3])*t^2)/Sqrt[2] (-I)*Sqrt[3/2]*t*U
((3*I)*t*U)/Sqrt[2] 0 ((3 - I*Sqrt[3])*t*U)/(2*Sqrt[2]) (-2 + (2*I)*Sqrt[3])*t^2 (-I/4)*(-5*I + Sqrt[3])*t*U (-I/4)*(-3*I + Sqrt[3])*U^2 -4*t*U ((I/2)*(3*I + Sqrt[3])*U^2)/Sqrt[2] 0 ((5 - I*Sqrt[3])*t*U)/4 0 0
0 ((3*I + Sqrt[3])*t*U)/2 4*t^2 ((3 - I*Sqrt[3])*t*U)/(2*Sqrt[2]) 0 ((1 + I*Sqrt[3])*t*U)/Sqrt[2] ((-I/2)*(-3*I + Sqrt[3])*U^2)/Sqrt[2] -5*t*U 0 0 0 0
-(((3*I + Sqrt[3])*t^2)/Sqrt[2]) -(Sqrt[3/2]*t*U)/2 0 (-I/2)*Sqrt[3]*t*U ((-4 - (4*I)*Sqrt[3])*t^2 + (1 - I*Sqrt[3])*U^2)/4 t*U 0 0 -2*t*U t^2*(-1 - I*Sqrt[3] - U^2/(2*t^2)) ((1 + I*Sqrt[3])*t^2)/Sqrt[2] (I/2)*Sqrt[3/2]*t*U
((3*I + Sqrt[3])*t*U)/(2*Sqrt[2]) 0 (t*(Sqrt[2]*U - (3*I)*Sqrt[6]*U))/4 (-I/4)*(-I + Sqrt[3])*U^2 (t*(U - (5*I)*Sqrt[3]*U))/4 (1 - I*Sqrt[3])*t^2 ((5 + I*Sqrt[3])*t*U)/4 0 t^2*(-1 + I*Sqrt[3] - U^2/(2*t^2)) -4*t*U 0 I*Sqrt[2]*(I + Sqrt[3])*t^2
(Sqrt[3]*t*U)/2 (-3*I + Sqrt[3])*t^2 0 0 0 ((1 - I*Sqrt[3])*t^2)/Sqrt[2] 0 0 ((1 - I*Sqrt[3])*t^2)/Sqrt[2] 0 -3*t*U (-I/4)*(-3*I + Sqrt[3])*U^2
0 ((3*I)/4)*t*U 0 -(t*U)/(2*Sqrt[2]) (Sqrt[2] + I*Sqrt[6])*t^2 I*Sqrt[3/2]*t*U 0 0 (-I/2)*Sqrt[3/2]*t*U (-Sqrt[2] - I*Sqrt[6])*t^2 (I/4)*(3*I + Sqrt[3])*U^2 (-15*t*U)/4