The verdict
If your problem is that answers live in too many places, pick Document360. It gives you approvals, collaborative editing and AI search that cites your articles. If your problem is that requests get lost in a shared inbox, pick Zendesk. It gives every request an owner and a status.
A small team with a few dozen articles should not buy either for the knowledge base alone. A page in a wiki or the help centre inside a helpdesk will do. Larger support teams may end up with both, because Document360 connects to Zendesk. Start with the tool that fixes the pain you feel this week. For most small B2B teams that is the ticketing problem, so Zendesk comes first, and Document360 follows once documentation becomes a real function.