Attosecond and nano-Coulomb electron bunches via the Zero Vector Potential mechanism von Timmis, RJL, Paddock, RW, Ouatu, I, Lee, J, Howard, S, Atonga, E, Ruskov, RT, Martin, H, Wang, RHW, Aboushelbaya, R, Leyen, MWVD, Gumbrell, E, Norreys, PA