One-pass solution

#include "stdafx.h"

void swap(int * array, int & left, const int right)
{
    while (array[left] != 0)
        left++;
    array[left] = array[right];
    array[right] = 0;
}

int moveZerosToTheLeft(int * array, const size_t len)
{
    int left = 0;
    for (int i = len - 1; i > left; i--) //now we start from the right until we reach the position of the last non-zero element
    {
        if (array[i] != 0) //Move this zero to the left side
            swap(array, left, i); //by swapping it with the leftmost zero
    }
    return left;
}

int main(void)
{
    int array[] = { 0, 1, 0, 2, 0, 0, 3, 4, 1, -23, 441, 0, -11, 2, 12, 1, 8, 0, 0 };
    int len = sizeof(array) / sizeof(array[0]);
    moveZerosToTheLeft(array, len);
}