Well you are doing it all wrong. Leave it to experts to test - all of which will shake head at your testing conditions. 1 miss or 1 hit dont make a perfect AV. They all have several of both.
Since you have 2 options you also have 2 programs to research. So do that. Will also tell you if it really is possible to make nod32 and Kav co-exist. Dont feel too sure just because there is no bsod. After 5 minutes you find out both are "highly recommended" - then you are supposed to install and test for your self. Now it is down to GUI and feelings
Take a look at AV-Comparatives and perhaps Wilders Security forums - though that can be bit too chatty at times. As I understand it AV-Comparatives is all about trust worthy testing environments (lack of same from just about every other test) - opposite them you have 1 sample and judge accordingly. Cant really go wrong since you have 2 of the best products but dont think you are testing... They also say over and over that there is much more to an AV than rigid numbers. How does it desinfect for example, options, customization, updates, resource usage etc. etc.
Not sure what Zonealarm product you have but I recently read their suits with all the goodies will receive updated Kaspersky code - very fast because the 2 companies should be more connected than is apparent. Money wize that is. Check out Zonealarm site and Kaspersky, probably best info at their user forums. Pretty good deal for the price, almost a bargain, but of course no use if it hogs whole computer. The real Kaspersky is not light by default that is for sure. Can be made to - if you make it work like Avira for example
Most is optional. Basic AV actions seems fast enough, all the extras especially Proactive stuff is very much active. Occasionally you feel it, have to work with excluded masks and trusted apps no matter tears. I dont know how much you can fiddle with Zonealarms version. I cant really see mini-Kaspersky being too heavy when you are happy with the big one? Cant be or you have run into a bug or whatever which will be fixed. Zonealarms KAV do get the very same updates as the real one Ive read so if you have paid license already may be try to work more with the suite instead of dumping it prematurely. I dont know it but assuming they have not messed up there is good value for monney - for those who need all included in the suite.
I just paid for 2 years license of Kaspersky but checked out trial versions of that and NOD32 first. Had no doubt what to get. Current detection I dont value that highly really. Overall they are both great. Paid more attention to GUI, options, support, general feel (probably the most important) - and a little bit to the beta in works. Nod32 is crap with GUI, Kaspersky almost elegant - just messed up here and there, until you read help files, heh. Can see the point in getting Avira and just forget about. Who needs popups of code injections? Kaspersky is almost a life commitment - but I guess security is so much better?