generic zip iterator for simple zipping in c++

zipper.cpp

#include <vector>
#include <tuple>
#include <iostream>

using namespace std;


template <
    typename T1,
    typename T2,
    template <typename> typename Container1,
    template <typename> typename Container2
    >
class zip_iterator
{
	using cont_t1 = Container1<T1>;
	using cont_t2 = Container2<T2>;
	using it_t1   = typename cont_t1::iterator;
	using it_t2   = typename cont_t2::iterator;
	using self_t  = zip_iterator<T1, T2, Container1, Container2>;

	it_t1 it1;
	it_t2 it2;
public:
	explicit zip_iterator(it_t1 fst, it_t2 snd) : it1{fst}, it2{snd} {}

	auto& operator++()
	{
		++it1; ++it2;
		return *this;
	}
	auto  operator++(int)
	{
		auto prev {this};
		++*this;
		return *prev;
	}

	bool operator!=(const self_t& other) const
	{
		return it1 != other.it1 && it2 != other.it2;
	}
	bool operator==(const self_t& other) const
	{
		return !operator!=(other);
	}

	pair<T1, T2> operator*() const
	{
		return {*it1, *it2};
	}
};


namespace std {
	template <
    	typename T1,
    	typename T2,
    	template <typename> typename Container1,
    	template <typename> typename Container2
    	>
	class iterator_traits<zip_iterator<T1, T2, Container1, Container2>>
	{
		using iterator_category = forward_iterator_tag;
		using difference_type   = long int;
		using value_type 		= pair<T1, T2>;
	};
};


template <
    typename T1,
    typename T2,
    template <typename> typename Container1,
    template <typename> typename Container2
    >
class zipper
{
	using cont_t1 	= Container1<T1>;
	using cont_t2 	= Container2<T2>;
	using it_t1   	= typename cont_t1::iterator;
	using it_t2   	= typename cont_t2::iterator;
	using it_t  	= zip_iterator<T1, T2, Container1, Container2>;

	cont_t1 &a;
	cont_t2 &b;
public:
	zipper(cont_t1 &fst, cont_t2 &snd) : a{fst}, b{snd} {}

	it_t begin() const { return it_t {std::begin(a), std::begin(b)}; }
	it_t end()   const { return it_t {std::end(a)  , std::end(b)  }; }
};


template <
    typename T1,
    typename T2,
    template <typename> typename Container1,
    template <typename> typename Container2
    >
auto make_zip(Container1<T1>& fst, Container2<T2>& snd)
{
	return zipper<T1, T2, Container1, Container2> {fst, snd};
}

int main()
{
	vector<int> a {1, 2, 3};
	vector<double> b {3.14, 2.92, 0.577, 1.292};
	vector<string> c {"s1", "s2"};

	for(auto [i, d] : make_zip(a, b))
	{
		cout << i << "--" << d << " ";
	}
	cout << endl;

	for(auto [i, s] : make_zip(a, c))
	{
		cout << i << "--" << s << " ";
	}
	cout << endl;

	return 0;
}