I didn't actually know much about virtual DJ until DJdecks made the announcement that they had actually merged operations with the commercial project/commercial product known as Virtual DJ. Sure its name didn't have the greatest of rings to it (in fact the name DJdecks was pretty lame and initially didn't actually make me want to buy it), but that aside having been a long time DJdecks user after reading many glowing reviews about it before hand, it seemed odd that they were shutting down the DJdecks project since DJdecks has full and very competent compatibility with many well known and well established DVS formats, even including the lesser known ones from back when DVS research development had one of the first usable and fully working DIY solutions used in actual clubs in the form of MsPinky. The better known DVS formats that DJdecks had compatibility with included the most recent iterations of Serato scratch, Final skratch, and Traktor skratch timecode vinyl or alternately the timecode CD equivalents. They even had their very own custom time-code for DJdecks boasting much higher timecode resolution then all the commercial DVS that DJdecks was actually fully compatible with. 

I've actually tested DJdecks first hand with the Z4 using Serato, and Traktor's time code vinyl, even with DJdecks very own timcode media via the pacemaker connected to the Z4 too. I can confirm it worked perfectly as a DVS when I used to use it heavily before making the full switch to Ableton Live. DJdecks as a pro solution allowed to me to achieve DVS latency times that were faster then any commercial packaged option on the market with near 100% "free of crashes" operation, that's how good it actually was. If it wasn't that good I would have ditched it a long time ago and buried it in a flaming discontented trashing and set a proverbial flaming paper bag down on their door step with dog turd in it. But like I said with near 100% reliability it pretty much worked perfectly without any problems at all for the main part.

I didn't know much about Virtual DJ however I could only imagine that with DJdecks and Virtual DJ's recent merger the Virtual DJ application would pretty much incorporate everything that had been researched, developed and engineered for the DJdecks project. 

This is also against the fact that there was never any kind of DJdecks support forum for the Z4 mixer the whole time I used DJdecks with the Z4. 

However there are now actual pages on the Virtual DJ forum that actually offer help and pointers about using the Z4 with Virtual DJ since the merger. This is the only reason I have included it on this Z4 page since its supposed to be about everything that is to do with the Z4 as it comes to mind. Am I saying that virtual DJ a sub-standard DVS option? Nope. Have I tested Virtual DJ since the merger? Nope. But I'm very inclined to think it should be of very high quality if it uses DJdecks high speed low latency core and DJdecks audio engine since the merger (despite the fact that DJdecks had a lame name). The merger also meant that DJdecks lost the muti-DVS format compatibility to now only have compatibility  with the "newly" developed virtual DJ DVS timecode. (most likely developed from the higher resolution DJdecks timecode which in turn allows for more accurate tracking)

I've also been made aware that Virtual DJ as a professional DJ application wasn't taken very seriously at all before the merger. I'm not sure what the standing of virtual DJ is post merger but I very much doubt its as crappy as it once used to be since the merger. If it wasn't for the fact that the "first hand tried and tested" DJdecks core is now actually used in Virtual DJ I would not even bother recommending Virtual DJ at all.

HOWEVER! If you know your hardware is 100% compatible with Traktor it might be an idea to check at their site first as they have half price discount offers from time to time that makes Traktor pro vastly cheaper to buy and own then Virtual DJ during the actual Native Instruments offer periods.

You can get more info about DJdecks by clicking this.