Firstly to begin with thier is a points system called the CAF ranking system devised by CAF which ranks countries. The points earn help countries to be ranked. The 12 AFRICAN countries with the most points get to have two teams each in CAF competition.
Currently those countries are Tunisia, Egypt, Congo DR, Algeria, Sudan, South Africa, Congo, Morocco, Ivory Coast, Mali, Cameroon and Nigeria.
Any club from a country which qualifies for the group stage of CAF competition earns points for doing that. The second part is about how a country earns points. Just to keep it simple; if you qualify for the group stage of the CAF African Champions league you will get 1 point for ending 4th and 2 points for finishing the group in third place and 5 points for becoming Champions.
The CAF Confederations also has a way it calculates the points. Now this is the most important part. The rankings are calculated every 5 years. Then each year is multplied by numbers 5 down to 1. I know some may get confused here, but it is simple. If Zesco United ends in the semi finals this year they earn 3 points (semi-final) multiplied by 5 and it will give 15 points.
Next year Zesco's 3 points will still be counted but it will be multpilied by 4 which will be 12 points. The next year it will be multiplied by three and until it reaches year 5 where if no zambian club has qualified for the group stage it will become 0 points.
So most important thing to note is that a club needs to earn points for its country to reach the TOP 12 and remain there.
and if no club earns points for its country they will come out of the top 12.
Now looking at Zesco United and the way they qualified this is what happened. For Zesco to get enough points it needed to surpass at least the two lowest ranked Countries in the CAF 5 year club ranking and these were Cameroon ( 12 Points) and Nigeria ( 13 Points).
Cameroon was number 12 and Zambia's job was made easier as no club from Cameroun qualified for the group stage this year and this means that they couldnt earn any other points aside from the 12 they already had.
Zambia already had 3 points earned by Nkana when they participated in the 2014 CAF confederations Cup group stage. So all Zambia needed was Zesco United to get 10 points to surpass Cameroon and earn 4 positions in 2018. For Zesco United, they only needed to avoid finishing last in the group.
Finishing in third position earns 2 points multiplied by 5 years which makes 10 points, and Zesco United not only exceeded 10 points but made it to the semi finals meaning more points for Zambia. As things stand in the 2018 season Zambia are ranked 9th Now.
So this is how Zesco United earned Zambia 2 more places in CAF competitions.
Hope the explanation is not to complicated as I cut out a lot of areas and wanted to keep it as simple as possible.
All in all as is expected we shall see the most exciting and competitive ZSL season in 2017 as clubs push for those 4 places.