def vol_zone(poly1, poly2):
    """"volume of a zone defined by two polygon bases """
    c_point = central_p(poly1, poly2)
    c_point = (c_point[0], c_point[1], c_point[2])
    vol_therah = 0
    num = len(poly1)
    for i in range(num-2):
        # the upper part
        tehrahedron = [c_point, poly1[0], poly1[i+1], poly1[i+2]]
        vol_therah += vol_tehrahedron(tehrahedron)
        # the bottom part
        tehrahedron = [c_point, poly2[0], poly2[i+1], poly2[i+2]]
        vol_therah += vol_tehrahedron(tehrahedron)
    # the middle part
    for i in range(num-1):
        tehrahedron = [c_point, poly1[i], poly2[i], poly2[i+1]]
        vol_therah += vol_tehrahedron(tehrahedron)
        tehrahedron = [c_point, poly1[i], poly1[i+1], poly2[i]]
        vol_therah += vol_tehrahedron(tehrahedron)
    tehrahedron = [c_point, poly1[num-1], poly2[num-1], poly2[0]]
    vol_therah += vol_tehrahedron(tehrahedron)
    tehrahedron = [c_point, poly1[num-1], poly1[0], poly2[0]]
    vol_therah += vol_tehrahedron(tehrahedron)
    return vol_therah
volume of a zone defined by two polygon bases