How to use one function handle to generate function handles returning different values?

For example, here is my function:

function [ fy, fz ] = funtest( x,a )
fy = x + 1 + a;
fz = x + 1 + a + 2*a;
end

We can see fy and fz are similar, so I do not want to write two functions for each of them respectively. I do not use the function to get function value. I want to get function handles. Such as, in command window, when I type in

a = 3; f1 = @(x)funtest(x,a)

something like this, and I have a function handle for fy. MeanWhile maybe

f2 = @(x)funtest(x,b)...

having a little bit modification for fz.

I tried

 f1 = @(x)funtest(x,a)(1)

for fy, and get an error "Error: ()-indexing must appear last in an index expression." And

 [f1, f2] = @(x)funtest(x,a)

gets an error "Error: Only functions can return multiple values." .

Any suggestion is appreciate. Have a beautiful day!