C++ assignment operator not printing proper values

Question

I have a class 3D point velocity which inherits from the 3D point and 3D velocity (not very well thought ). Just testing C++ concepts. The issue is that when I print the values from the sum, it prints out the garbage value. Not sure why I have added the logs in the functions. Values look good, but still, the sum is printing invalid values. Code:

//
// Created by xyz on 8/28/2022.
//

#include <iostream>

class my3Point {
public:
    int _x, _y, _z;
    my3Point() : _x(0), _y(0), _z(0) {}
    my3Point(int a, int b, int c) : _x(a), _y(b), _z(c) {
        // std::cout<<"x: "<<a<<", y: "<<b<<", z: "<<c<<std::endl;
        // std::cout<<"x: "<<_x<<", y: "<<_y<<", z: "<<_z<<std::endl;
    }
    my3Point(my3Point &rhs){
        _x = rhs._x; _y = rhs._y; _z = rhs._z;
    }
    my3Point& operator+(my3Point&rhs){
        std::cout<<"Inside the addition of my 3D point"<<std::endl;
        _x += rhs._x;
        _y += rhs._y;
        _z += rhs._z;
        std::cout<<"x: "<<_x<<", y: "<<_y<<", z: "<<_z<<std::endl;
    }
};

class my3Velocity {
public:
    int _vx, _vy, _vz;
    my3Velocity() : _vx(0), _vy(0), _vz(0) {}
    my3Velocity(int a, int b, int c) : _vx(a), _vy(b), _vz(c) {
        //std::cout<<"x: "<<_vx<<", y: "<<_vy<<", z: "<<_vz<<std::endl;
    }
    my3Velocity(my3Velocity &rhs){
        _vx = rhs._vx; _vy = rhs._vy; _vz = rhs._vz;
    }
    my3Velocity& operator+(my3Velocity&rhs){
        std::cout<<"Inside the addition of my 3D Velocity"<<std::endl;
        _vx += rhs._vx;
        _vy += rhs._vy;
        _vz += rhs._vz;
        std::cout<<"x: "<<_vx<<", y: "<<_vy<<", z: "<<_vz<<std::endl;
    }
};

class my3VelocityPoint: public my3Point, public my3Velocity {
public:
    int acc; //accerlation
    my3VelocityPoint() : my3Point(), my3Velocity(), acc(0) {}
    my3VelocityPoint(int a1, int a2, int a3, int b1, int b2, int b3, int c) : my3Point(a1, a2, a3), my3Velocity(b1, b2, b3), acc(c) {}
    my3VelocityPoint& operator+(my3VelocityPoint&rhs){
        my3Point::operator+(rhs);
        my3Velocity::operator+(rhs);
        acc += rhs.acc;
        std::cout<<"Inside the addition of my 3D velocity point"<<std::endl;
    }
    my3VelocityPoint& operator=(my3VelocityPoint &rhs){
        if (this == &rhs){
            return *this;
        }
        _x = rhs._x; _y = rhs._y; _z = rhs._z;
        _vx = rhs._vx; _vy = rhs._vy; _vz = rhs._vz;
        acc = rhs.acc;
        std::cout<<"Inside operator = "<<std::endl;
    }
    void print();
};

void my3VelocityPoint::print() {
    std::cout<<"Position: \n";
    std::cout<<"x: "<<_x<<", y: "<<_y<<", z: "<<_z<<std::endl;
    std::cout<<"Velocity: \n";
    std::cout<<"x: "<<_vx<<", y: "<<_vy<<", z: "<<_vz<<std::endl;
    std::cout<<"Accerlation: \n";
    std::cout<<"x: "<<acc<<std::endl;
}


int main()
{
    /*
    my3Point myPoint;
    my3Velocity myVelocity;
    my3VelocityPoint myVelPoint;
    std::cout<<"SIZES: "<<std::endl;
    std::cout<<"3D Point: "<< sizeof(my3Point)<<std::endl;
    std::cout<<"3D Velocity: "<< sizeof(my3Velocity)<<std::endl;
    std::cout<<"3D Velocity Point: "<< sizeof(my3VelocityPoint)<<std::endl;

    std::cout<<"ADDRESSES: "<<std::endl;
    std::cout<<"3D Point: "<< &myPoint<<std::endl;
    std::cout<<"3D Velocity: "<< &myVelocity<<std::endl;
    std::cout<<"3D Velocity Point: "<< &myVelPoint<<std::endl;
    std::cout<<"Vel x: "<<&(myVelPoint._x)<<", y "<<&(myVelPoint._y)<<", z: "<<&(myVelPoint._z)<<std::endl;
    std::cout<<"Vel vx: "<<&(myVelPoint._vx)<<", vy "<<&(myVelPoint._vy)<<", vz: "<<&(myVelPoint._vz)<<std::endl;
     */

    my3VelocityPoint myVelPoint1(0,0,0, 1, 1, 1, 5), myVelPoint2(3,0, 0, 3, 4, 5, 10);
    myVelPoint1.print(); myVelPoint2.print();
    my3VelocityPoint sum;
    // sum.print();
    sum = myVelPoint1 + myVelPoint2;
    sum.print();
    /*
    void* myAddr = &myPoint;
    std::cout<<"Address of class: "<<myAddr<<std::endl;
    std::cout<<"Address of class: "<<&(myPoint._y)<<std::endl;
     */

    return 0;
}