By definition, the TOM = DOM + USEFUL LOAD. The fact
that the TOM is 64280 and DOM is 35000, USEFUL LOAD must be 29280. So the other
figures are red herrings I think.
If you work it this way ZFM = 52080; and ZFM = DOM + (USEFUL LOAD-FUEL) so you
could say TOM - ZFM = FUEL, which works out as 12200kg.
Rearranging: ZFM = DOM + (USEFUL LOAD-FUEL)
ZFM-DOM+FUEL = useful load
52080-35000+12200=29280
So it does give the same value. The reason the values aren't limiting is that
it is not MZFM and MTOM, they are just stated as facts that they are the actual
values.