Count zeros - system does not accept the solution

Hello, I don’t understand why the code I wrote is not accepted by the system:
/**************************************************/
using System;

namespace ParametersToMethods

{

class HowManyZer0s

{

    static void Main()

    {

        string inputString = Console.ReadLine();

        int numberOfZeros;

        if (AnalyzeString(inputString, out numberOfZeros))

        {

            Console.WriteLine(numberOfZeros);

        }

        if (!AnalyzeString(inputString, out numberOfZeros))

        {

            Console.WriteLine("The string is invalid.");

        }

    }

    static bool AnalyzeString(string input, out int zeros){

        zeros = 0;

        if (String.IsNullOrEmpty(input))

        {

            return false;

        }

        for (int i = 0; i < input.Length; i++)

        {

            if (input[i] == '0')

            {

                zeros++;

            }

        }

        return true;

    }      

}

}
/**************************************************/

The console output is correct but the system just does not accept the solution for some reason.

thanks a lot

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