Zeros are points on the graph that are x-intercepts; in the graph we can see that they cross -2 and 1 on the 1st equation, -1 and 3 on the 2nd equation, -3 and 1 in the 3rd equation, and -1 in the 4th equation. Since it intersects no x-intercepts in the 5th and 6th equation, it has no zeros.