if your fuses are really set to zero the chip is dead and theres nothing you can do short of buying an expensive programmer with 12v capability. try just reading the fuses. that is always safe. if the signature reads ok that means your fuse is not really zero. if you didnt use the -u before then it is not likely fuses were changed to zero. one must be very careful when changing fuses because that is the #1 way noobs brick their avr.