Matrix t2*K(2) in Subspace 58 with Dimension 12

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

-(((29 + 9*Sqrt[6])*t*U)/(6 + Sqrt[6])) -(Sqrt[5/6]*t*U) 0 0 0 ((Sqrt[2] - 3*Sqrt[3])*t*U)/Sqrt[6 + Sqrt[6]] (Sqrt[6 + Sqrt[6]]*t*U)/2 (-4*(1 + Sqrt[6])*t^2)/Sqrt[6 + Sqrt[6]] 0 0 0 0
-(Sqrt[5/6]*t*U) ((-83 + 38*Sqrt[6])*t*U)/(12 - 7*Sqrt[6]) 0 0 0 (Sqrt[2/(6 - Sqrt[6])] + 3*Sqrt[3/(6 - Sqrt[6])])*t*U (-3*(Sqrt[2] - 2*Sqrt[3])*t*U)/(2*Sqrt[18 - 3*Sqrt[6]]) (4*(-1 + Sqrt[6])*t^2)/Sqrt[6 - Sqrt[6]] 0 0 0 0
0 0 (-15*t*U)/2 (3*t*U)/Sqrt[2] 0 -(Sqrt[3/2]*t*U) (Sqrt[3]*t*U)/2 0 0 (Sqrt[3]*t*U)/2 -(Sqrt[3/2]*t*U) -(Sqrt[3]*U^2)/2
0 0 (3*t*U)/Sqrt[2] -6*t*U 0 0 0 -2*Sqrt[6]*t^2 0 -(Sqrt[3/2]*t*U) -(Sqrt[3]*t*U) -(Sqrt[3/2]*U^2)
0 0 0 0 -4*t*U -U^2 -2*Sqrt[2]*t^2 -(Sqrt[2]*t*U) t*U -2*Sqrt[2]*t^2 0 Sqrt[2]*t*U
((Sqrt[2] - 3*Sqrt[3])*t*U)/Sqrt[6 + Sqrt[6]] (Sqrt[2/(6 - Sqrt[6])] + 3*Sqrt[3/(6 - Sqrt[6])])*t*U -(Sqrt[3/2]*t*U) 0 -U^2 -2*t*U (t*U)/Sqrt[2] 0 0 (-3*t*U)/Sqrt[2] -2*t*U 0
(Sqrt[6 + Sqrt[6]]*t*U)/2 (-3*(Sqrt[2] - 2*Sqrt[3])*t*U)/(2*Sqrt[18 - 3*Sqrt[6]]) (Sqrt[3]*t*U)/2 0 -2*Sqrt[2]*t^2 (t*U)/Sqrt[2] (-11*t*U)/2 -U^2 (4*t^2 - U^2)/Sqrt[2] (3*t*U)/2 -(Sqrt[2]*t*U) -4*t^2
(-4*(1 + Sqrt[6])*t^2)/Sqrt[6 + Sqrt[6]] (4*(-1 + Sqrt[6])*t^2)/Sqrt[6 - Sqrt[6]] 0 -2*Sqrt[6]*t^2 -(Sqrt[2]*t*U) 0 -U^2 -4*t*U 0 0 2*Sqrt[2]*t^2 0
0 0 0 0 t*U 0 (4*t^2 - U^2)/Sqrt[2] 0 -7*t*U 2*Sqrt[2]*t^2 0 (t*U)/Sqrt[2]
0 0 (Sqrt[3]*t*U)/2 -(Sqrt[3/2]*t*U) -2*Sqrt[2]*t^2 (-3*t*U)/Sqrt[2] (3*t*U)/2 0 2*Sqrt[2]*t^2 (-9*t*U)/2 (5*t*U)/Sqrt[2] t^2*(-4 + U^2/(2*t^2))
0 0 -(Sqrt[3/2]*t*U) -(Sqrt[3]*t*U) 0 -2*t*U -(Sqrt[2]*t*U) 2*Sqrt[2]*t^2 0 (5*t*U)/Sqrt[2] -4*t*U U^2/Sqrt[2]
0 0 -(Sqrt[3]*U^2)/2 -(Sqrt[3/2]*U^2) Sqrt[2]*t*U 0 -4*t^2 0 (t*U)/Sqrt[2] t^2*(-4 + U^2/(2*t^2)) U^2/Sqrt[2] (-3*t*U)/2