Zeiss 24mm really worth it?

It's not worth the money vs the Sigma's. If you get the Sigma 19, 30 + 50, which you can get for the price of the Zeiss 24, then you've got an excellent system that's really versatile.

But - the Zeiss is also excellent, so I'd say get the others first to get a complete system then add the Zeiss if you want after.