I am afraid the max. landing weight (or mass, if You prefer) is only one of the limiting factors.
With ZFW and fuel burn known, Your takeoff fuel can be limited by either one of the following (not looking at the distinct possibility of a high ZFW not allowing to fuel as required and therefore necessitating offloading of payload):
-structural max. TOW
-performance limited max. TOW
-structural MLW -performance limited MLW.
-fuel tank capacity.
So the maximum fuel You can have on board at the beginning of takeoff is the lowest number of the following calculations:
a. MATOW - ZFW
b. MALAW - ZFW + burnoff.
c. maximum fuel tank capacity - taxi fuel.
As You will typically stand on the ramp when the decision for uplift is to be made, the taxi fuel needs to be minded as well, and therefore the maximum ramp weight comes into play.
So the fuel on board will need to be equal to or less than the lowest of following:
a (from above) + taxi fuel
b + taxi fuel
c.
And from there on it is easy - the maximum uplift is max. FOB minus the fuel that You already have in the tanks.
For everything else, see the flight planning instructions in Your company OM-A and OM-B...