Command (e.g. `g++`) does not point to the same binary when run from the terminal or from (neo)vim

Question

I have NVIM v0.4.3 on macOS Mojave version 10.14.6 I have different version of g++ compilers on my machine and made the following alias in my .zshrc file:

alias g++="/usr/local/bin/g++-9"
alias g++Old="/usr/bin/g++"

I want to compile and run the following script on my Mac that I named count6.cpp:

#include <iostream>
#include <vector>

using namespace std;

int main()
{
    vector<int> vec;
    vec.push_back(11);
    vec.push_back(1);
    vec.push_back(8); // vec{4, 1 8}
    for(auto elem: vec)
        cout << elem << " ";
    return 0;
}

If I run the command the

g++ count6.cpp -o count6; ./count6

I get the following output:

11 1 8 %

However if I type the same command from within nvim, I get the following warnings:

:!g++ count6.cpp -o count6; ./count6
count6.cpp:12:9: warning: 'auto' type specifier is a C++11 extension [-Wc++11-ex
tensions]
    for(auto elem: vec)
        ^
count6.cpp:12:18: warning: range-based for loop is a C++11 extension [-Wc++11-ex
tensions]
    for(auto elem: vec)
                 ^
2 warnings generated.
11 1 8

Ny interpretation is that the command from within nvim does not point to the same binary. How can I make point to the same binary?