i have brought quite a few batteries back from low voltage but if it was zero volts then it is guaranteed to be damaged and lost capacity. check for swelling and charge slowly with a balance on. check voltage on each cell very often. any cell with over 4.2v is dangerous. if you can get the battery full charged and balance with all cells at 4.2v then you can try to use it some but be careful of voltage drop. check the cell that was at zero every minute while discharging and see if the voltage has dropped to 3.0v or less. most likely it will do this much earlier than any other cell in the pack. the best thing to do if it doesnt hold as much capacity as it needs to be useful is to remove the bad cell and make it a 3s pack if the bad cell is on the end of the pack and you have good soldering skills.

the things i check to see if a cell is "healthy" are: is voltage between 3.0-4.2v, does the cell stay cool while charging, is the cell nice and flat (no puffing/swelling and no bends or physical damage).

some more advanced stuff is if the voltage is nice and steady during charge and discharge and is the capacity 80% or better of original rating. you have to watch the screen on your triton to see this stuff.