I want to to return in main

void arith::tp()
{
  int z;
  float x, y;
  do
  {
    cout << endl
      << " 1 -> Addition + \n"
      << " 2 -> Subtraction - \n"
      << " 3 -> Multiplication * \n"
      << " 4 -> Division  / \n"
      << " 5 -> Squared x^2 \n"
      << " 6 -> Calculation 1/x \n"
      << " 7 -> Square Root \n"
      << " 8 -> Per Cent \n"
      << " 0 -> Exit \n"
      << " Give a choice: ";
      cin >> z;
      // ...
   } while ( z != 0);
  // here the method exits and control returns to the calling code (main)
}

i dont know how to do this thanks

NoNobody knows what exactly you want to know when you ask for "this".

Just aother guess:
To call a member function you first have to declare the class

// demo1.cpp : Console application
#include <iostream>

class arith {
public:
	void tp();
};

using namespace std;

// Hi i have create this Function:

// Tupikh Xrhsh
void arith::tp()
{
	int z;
	do {
		cout << endl
			<< " 1 -> Addition + \n"
			<< " 2 -> Subtraction - \n"
			<< " 3 -> Multiplication * \n"
			<< " 4 -> Division  / \n"
			<< " 5 -> Squared x^2 \n"
			<< " 6 -> Calculation 1/x \n"
			<< " 7 -> Square Root \n"
			<< " 8 -> Per Cent \n"
			<< " 0 -> Exit \n"
			<< " Give a choice: ";
		cin >> z;
	} while (z != 0);
}

// 	when choice the 0 i want to return in main

The code was already in main, just copy & paste.

int main()
{
	int ep;
	arith run;
	do {
		cout << endl
			<< " 1 -> Tupikh Xrhsh \n"       // stupid Xrnsh
			<< " 2 -> Epistimonikh Xrhsh \n"  // scientific Xrnsh
			<< " 3 -> Isotimia Nomismatos \n"
			<< " 4 -> Thermokrasia \n"
			<< " 5 -> Mhkos \n"
			<< " 6 -> Varos \n"
			<< " 7 -> Xronos \n"
			<< " 0 -> Exit \n"
			<< " Dwse mia epilogh: ";
		cin >> ep;
		switch (ep) {
		case 1:	run.tp();
				break;
		}


	} while (ep != 0);
	return 0;
}

Last thing is to call the memberfunction and job is done.