Converting syms to double

Hi, I'm trying to solve for multiple phase shifts using syms. However, when I try to convert to a double in my last switch, I get the error: "Conversion to 'sym' from 'struct' is not possible". I assumed it was because it was trying to use angles between -inf to inf, but after forcing it to assume that phi and theta were between -pi and pi, it still wouldn't allow me to see the values of my angles. I think I might be overcomplicating this. Can someone help me please?

i=sqrt(-1);

%Basic spin 1 kets
zket(:,1)=[1;0;0];
zket(:,2)=[0;1;0];
zket(:,3)=[0;0;1];
xket(:,1)=[.5;1/sqrt(2);.5];
xket(:,2)=[1/sqrt(2);0;-1/sqrt(2)];
xket(:,3)=[.5;-1/sqrt(2);.5];
yket(:,1)=[.5;i/sqrt(2);-.5];
yket(:,2)=[1/sqrt(2);0;1/sqrt(2)];
yket(:,3)=[.5;-i/sqrt(2);-.5];

%Basic spin 1 bras
zbra=conj(zket');
xbra=conj(xket');
ybra=conj(yket');

Unknown1=[.25,1,.25;.5,0,.5;.25,0,.25];
Unknown2=[.55,.865,.25;.45,.130,.5;.05,.005,.25];
Unknown3=[.15,.03,(1/3);.7,0,(1/3);.15,.97,(1/3)];
Unknown4=[.25,.25,.5;.5,.5,0;.25,.25,.5];

 for Part=1:4
    switch Part
        case 1
            Psi=Unknown1;
        case 2
            Psi=Unknown2;
        case 3
            Psi=Unknown3;
        case 4
            Psi=Unknown4;
    end
    a(Part)=sqrt(Psi(1,3));
    b(Part)=sqrt(Psi(2,3));
    c(Part)=sqrt(Psi(3,3));
    syms theta phi
    assume(theta>=-pi);
    assumeAlso(theta<=pi);
    assume(phi>=-pi);
    assumeAlso(phi<=pi);
    Newb=b(Part)*exp(i*theta);
    Newc=c(Part)*exp(i*phi);
    NewPsi=a(Part)*zket(:,1)+Newb*zket(:,2)+Newc*zket(:,3);

    XZERO=(xbra(2,:)*NewPsi)*conj(xbra(2,:)*NewPsi);
    XNEG=(xbra(3,:)*NewPsi)*conj(xbra(3,:)*NewPsi);
    YZERO=(ybra(2,:)*NewPsi)*conj(ybra(2,:)*NewPsi);
    YNEG=(ybra(3,:)*NewPsi)*conj(ybra(3,:)*NewPsi);

    SolnsZero=solve(Psi(2,1)==XZERO,Psi(2,2)==YZERO,theta,phi)
    SolnsNeg=solve(Psi(3,1)==XNEG,Psi(3,2)==YNEG,theta,phi)

    switch Part
        case 1
            Zero1=subs(SolnsZero)
            Neg1=subs(SolnsNeg)
        case 2
            Zero2=subs(SolnsZero)
            Neg2=subs(SolnsNeg)
        case 3
            Zero3=subs(SolnsZero)
            Neg3=subs(SolnsNeg)
        case 4
            Zero4=subs(SolnsZero)
            Neg4=subs(SolnsNeg)
    end
 end