Both, but mostly DJing. Normally I only use the Arturia keyboard and the iPad with a sequencer so great beats, but some time it is also fun to use the build-in effects of the Korg to mangle synth and drumsounds.
Zero 4 is a pretty sweet mixer, it has a build-in soundcard and built-in digital effects. The build quality of the mixer is also pretty good, only the knobs are a bid wobbly since they are made from plastic but do respond very well.
What I do really like is the fact you midi map the effect knobs, I got them mapped to Ableton effect and send knobs.