Bringing gemstones from Madagascar to an auction house in Switzerland [closed]

I intend to travel to Madagascar in the next couple of months. I am interested in buying gemstones there and bringing the gemstones to Switzerland to sell them through an auction house based there. I am interested in what is the legal way to do this.

My flight itinerary will be from Zurich International Airport to Antananarivo with a connecting flight at CDG Airport in Paris and my returning flight will be through the same route.

When returning, will I have to go through customs at ZRH or CDG, or both?

Will I have to do the customs formalities only at the final destination, or in France also?

The auction house's website reads that they will arrange customs formalities for people who bring their stuff to them from sale from overseas (I am not from Switzerland). When I arrive at ZRH with the gemstones, how will the customs procedures be done? Wath will I have to do? Can I store the gemstones at a bonded customs warehouse until I can contact the auction house and arrange with them to do the customs formalities for me?

Do I have to notify Swiss customs that I bring the gemstones with me in advance, or do I only have to tell them once I arrive at ZRH Airport?

Please give me some advice as to how to go about this. I am only interested in doing this the legal way, of course.

Thank you very much in advance!