Zachman is an enterprise architecture framework. Enterprise architecture is higher level than what people generally think about when they say "software architect." YOu definitely don't need to know it at first. Later on, it depends on the size/scale of your company and how you fit in.
Nothing like UML. UML is an application level concept. Enterprise architecture is higher level. I don't know how to explain it well, but look at the diagrams on wikipedia. You can see organizational concerns here rather than things that apply to a specific application.