In reply to Timmd:
> every bit of Decathlon gear I've ever had which has had a zip in it has failed within a couple of years
I think you're either unlucky, or heavy on gear.
Decathlon use YKK zips, like most other manufacturers. Checking two Decathlon down jackets, they both use 5C zips, as does my Alpkit Filo. Checking a light Decathlon soft shell jacket, it too uses a 5C zip, as do a Rab VR Flex jacket and a Patagonia Ready Mix jacket, both similar weight jackets.
Yes, I do have too much stuff...