Is this the right place to have a discussion about rule 4? I think we need to talk about it as a community, now that de_zenith has exemplified how problematic it is.
I can understand wanting a simple set of rules that you can follow religiously, so admins don't have to decide subjectively on a case-by-case basis. That being said, you cannot always write a rule that covers all cases of right or wrong correctly. In this case, I think that rule 4 is exceptionally far from covering what most people would think of as ok.
Taking de_zenith as an example (although I want to clarify that this is about the rule/the enforcement of it, not specifically about de_zenith), it seems that the map was basically finished before the contest started. I don't think there's any arguing that it has a huge advantage over other contest entries, since so much more time and work has been put into it.
I don't particularly want to argue about whether de_zenith should be removed from this contest, but I do think that we need to have a talk about what to do about cases like this in the future. It's clear that it isn't fair to have a map that's been developed for several years compete against one that's been developed for a couple of months - and we need to find a way to either change rule 4, or the way it's enforced, so it doesn't happen in future contests.