with havoline you will end up with a perfect mix of 50% in the system, with the ZIC super, you will end up with something like 30%
all you need to do with concentrate is (assuming your system holds 4 litres)
after cleaning system, let it drain out as much as it can, measure what came out, if its more than 50% (2 litres) of the systems total capacity then you open up the two concentrate bottles you bought and pour them in directly, then top up with water and start the engine, till the thermostat pops open or starts to pop open, let it bleed out any air. - cap it and you are done.
With premix you will always end up with less than 50% mixture as the already premixed coolant will mix with water already present in the system. To raise the concentration again you will need to buy another large container of premix and waste the old weaker premix unless you can find the same coolant as concentrate.
btw - the ZIC coolant is more expensive than havoline as you only get 1.5 litres of coolant concentrate for Rs 2610/- with buying the ZIC coolant, (water is free/almost free) while with the havoline you only pay Rs 2532/- for 2 litres concentrate coolant (which yields 4 litres)
So - in a nutshell, you could have spent Rs 2532/- (plus some clean water) and have 4 litres of ready to use coolant. while you spent Rs 2610/- and only got 3litres of ready use coolant, that too of inferior quality. (seems like shopkeeper made a nice sale (they get paid more by ZIC than by Havoline/Chevron).
in short
ZIC charging you Rs 2610/- for 3 litres ready mix actually cost you Rs 1740/- per litre concentrate (there is only 1.5 litres concentrate in that bottle))
Havoline is available for Rs 1266/- per litre concentrate.
But its your money - you may wish to spend as you wish,