I don't know about DAX, but CAC40 is pronounced in French like it's a word. Something like kɑk and then quarante (forty in French).
Search for videos on youtube, and you'll hear native speakers pronounce it.
I've heard the DAX pronounced on Marketplace (a business/financial show on NPR) as "Dacks." Rhymes with stacks.
Don't know how to pronounce Dacks, but DAX = ducks
Interesting. Where are you from?
Germany. And actually you're right with Dacks (or even Dachs), but only if you pronounce it as a german would do. I assume you pronounce it more like (M)acs?
Don't know how to pronounce Dacks, but DAX = ducks