How to add two different surface curves in a single plot?

[X,Y] = ndgrid(-3:0.1:3);
f  = @(x,y) exp(-(x.^2+(2*y).^2)*0.5);
Z = f(X,Y)*3;

figure
surf(X, Y, Z)
hold on
surf(X, Y, ones(size(Z)), 'FaceColor','r', 'FaceAlpha',0.5, 'EdgeColor','none')
hold off
colormap(turbo)

 

 

 

figure
[c,h] = contour(X, Y, Z, [1 1]);
axis('equal')
grid
Ax = gca;
Ax.XAxisLocation = 'origin';
Ax.YAxisLocation = 'origin';
elpsfcn = @(b,xy) xy(1,:).^2/b(1)^2 + xy(2,:).^2/b(2)^2 - b(3);
opts = optimoptions('fminunc', 'MaxFunctionEvaluations', 5E+3, 'MaxIterations',1E+4);
[B, fv] = fminunc(@(b) norm(elpsfcn(b,c(:,2:end))), rand(3,1), opts)

Local minimum possible.

fminunc stopped because it cannot decrease the objective function
along the current search direction.
B = 3×1
   52.8204
   26.4510
    0.0008
fv = 1.2653e-05

fprintf('Semimajor Axis = %.4f\nSemiminor Axis = %.4f\nConstant       = %.4f\n', B)

Semimajor Axis = 52.8204
Semiminor Axis = 26.4510
Constant       = 0.0008

text(-2.5, 2.5, sprintf('$\\frac{x^2}{%.2f^2} + \\frac{y^2}{%.2f^2} = %.4f$',B), 'Interpreter','latex', 'FontSize',16)