Nope, leastways I can't think of a way to use zeners.
If you just want to drop the voltage down the easiest way is to use 45 voltage dividers, all set to provide the best range possible for the voltage at that point in the battery string.
The voltage divider approach obviously loses resolution the further you need to drop the voltage - I don't know what resolution is needed here, but there must come a point where the voltage is so high that it isn't possible to achieve enough resolution.
I was thinking with the zener something like connecting each battery junction to a zener and then through a voltage divider to ground, the idea being that the zener would drop the voltage by a known constant amount to bring the voltage down to a range that can be measured, with no loss of resolution.
By the time you have several cells in series all with varying voltages the range of values that needs to be measured could easily exceed 5V hence the voltage dividers to reduce the range - still some loss of resolution due to the voltage dividers used for that, but nothing like as much as there would have been if dividers were used to drop the full voltage down to 5V.