You go by max allowed gross loaded weight of car, with a Zaf probably under 2tonnes so should be ok with caravan on B licence but you need to check. Towbar fitted to car can tow whatever car can tow.
If Zaf is 05-10 1.9d then gross weight is 2195kg + your caravan 1300kg = 3495kg so just towable on a B licence so ok. Caravan must have gross loaded weight, ie mtplm of no more than 1300kg.
The mass in running order (MIRO) is the weight when of the caravan when leaves the factory. It's the Maximum Technical Permissable Laden Mass (MTPLM) you need to calculate the towing weight on which can be found below the caravan door. The MTPLM minus the MIRO equals the payload which is the total weigh allowance for carrying the rest of the items such as gas cylinders, a battery, electric hook up leads, water barrels, waste container, cooking utensils and cutlery plus anything else you may want to carry such as chairs and an awning etc.
To work out a safe caravan match you need to find out the Zafira's kerbweight first and then using an online percentage calculator you need to find out what 85% is of that figure which will give you a guide as to what weight caravan you will be looking for which is the MTPLM figure (not the MIRO).
Yeah lots of sellers state the caravans unladen weight or MIRO.
You need to be really careful and check to see if your V5C or chassis plate has teh cars gross laden weight.
There should be at least 3 weights, Gross laden weight and axle weights. There maybe a gross trainweight figure also.