Question: How to simplify an output in maple (cotton tensor)

with(Physics);
Setup(mathematicalnotation = true):
Setup(dimension = 3, coordinates = (X = [x, y, t]), metric = -ut^2*(dx^2)+ut^2*(dy^2)+(-ux^2-uy^2+1)*(dt^2)+2*ux*ut*dx*dt+2*uy*ut*dy*dt):
              ut := Physics:-diff(u(X), t)
ux := diff(u(x, y, t), x);
                  ux := Physics:-diff(u(X), x)
uy := diff(u(x, y, t), y);
                  uy := Physics:-diff(u(X), y)
Define(S[mu, nu] = 1/(d-2)*(Ricci[mu, nu]-1/(2*d-2)*Ricci[`~alpha`, alpha]*g_[mu, nu]));
             Defined objects with tensor properties
Define(C[mu, nu, rho] = D_[nu](S[rho, mu])-D_[rho](S[nu, mu]));
             Defined objects with tensor properties
g_[];
Physics:-g_[mu, nu] = 

 
C[mu, nu, rho, nonzero];
          [Length of output exceeds limit of 1000000]
utt := diff(u(x, y, t), t, t);
               utt := Physics:-diff(u(X), t $ 2)
uxx := diff(u(x, y, t), x, x);
               uxx := Physics:-diff(u(X), x $ 2)
uyy := diff(u(x, y, t), y, y);
               uyy := Physics:-diff(u(X), y $ 2)
uxt := diff(u(x, y, t), x, t);
                uxt := Physics:-diff(u(X), t, x)
uyt := diff(u(x, y, t), y, t);
                uyt := Physics:-diff(u(X), t, y)
utt = ut*ut*(1/(-ux^2-uy^2+1))*(uxx+uyy)-2*ut*(1/(-ux^2-uy^2+1))*(ux*uxt+uy*uyt);
Basically here the cotton tensor exceeds the output limit in maple, however I am supposed to be showing how the cotton tensor vanishes, the last part of the code is me trying to input a relation of u_tt to various other derivatives of u in the hope that the cotton tensor can be simplified from this equation but nothing has changed as a result, can anyone help me?