Solving numerically nonlinear equation using fzero or fsolve with integral function inside

Dear all,.. Guys, I want to solve a value which is "a" in this case, in a very complex function with integral function inside it. for simplicity the func is something like this, a*A + a*B = integral(f(a)) + integral(g(a))

I try this code but it wasn't work, please help me.

syms x a
t0 =0;
t1 =1;
beta_0  = -1.08258e-8;
beta_1  = 1.881944374742801e-13;
beta_2  = 1.354999949814817e-11;
beta_3  = 4.319072657166946e-15;
R       = 1e-9;
alpha   = -1.6e-6; %assuming low temp room
dT      = 0; %assume constant temp @ room temp 
V_dc    = 60;

psi1 = 4.731119415901211;
psi2 = 9.611040163439666e+03;
psi3 = - 4.731118843460321;
C1_div = 0.015786826203739;

C1 = 1 ;
C2 = -0.015510886909126 /C1_div;
C3 = -0.015788256979393 /C1_div;
C4 = 0.015495280230272 /C1_div; 
C5 = -0.706760502482255 /C1_div; 
C6 = -0.706760502482188 /C1_div;

phi = C1*cosh(psi1*x)+C2*sinh(psi1*x)+C3*cos(psi3*x)+C4*sin(psi3*x)+C5*exp(-psi2*x)/(psi2^2)+C6*exp(psi2*x - psi2)/(psi2^2);
dif1_phi = diff(phi,x,1);
dif2_phi = diff(phi,x,2);
dif3_phi = diff(phi,x,3);
dif4_phi = diff(phi,x,4);
dif5_phi = diff(phi,x,5);
dif6_phi = diff(phi,x,6);

A_temp  = beta_0 *dif6_phi * phi;
A_fun   = matlabFunction(A_temp);
A       = integral(A_fun,0,1);

B_temp  = dif4_phi*phi;
B_fun   = matlabFunction(B_temp);
B       = integral(B_fun,0,1);

C_temp  = dif1_phi^2;
C_fun   = matlabFunction(C_temp);
C       = integral(C_fun,0,1);

d       = 500e-9;
b_0     = 100e-9;
w_0     = b_0/d *sin(pi*x);
dw_0    = diff(w_0,x);
d2w_0   = diff(w_0,x,2);
D_temp  = 2*dif1_phi*dw_0;
D_fun   = matlabFunction(D_temp);
D       = integral(D_fun,0,1);
epsi_0  = 8.854187817e-12; %vacum permitivity

E_temp  = (beta_2*alpha*dT + beta_1*(C*a^2-a*D))*(a*dif2_phi-d2w_0)*phi ;
E_fun   = matlabFunction(E_temp);
F_temp  = beta_3*V_dc^2 * phi /(sqrt((1-a*phi-w_0)*(1-a*phi-w_0+2*R))*(acosh(1/R + (1-a*phi-w_0)/R))^2);
F_fun   = matlabFunction(F_temp);
solving_a = @(a) a*A + a*B - integral(E_fun,0,1) - integral(F_fun,0,1);
a = fzero(solving_a,0)