system
Given the following post, respond as if you're commenting on Reddit:
human
[The Man In The High Castle] Why did the Nazis put a neutral zone over the US uranium deposits?

While the extent of uranium reserves was a surprise, the surface deposits were known about, and the Japanese actually did the original pre-war surveys.
gpt
Maybe both powers want the uranium, and open conflict is not an option. German Empire vs. Japanese Empire is basically the new Cold War, since the US and USSR aren't in the game anymore.

Look how US and USSR were "Allies" during WWII, but became enemies later. The alliance of Japan and Germany in the alternate universe is more amiable, but still they both want the whole world.

They just can't risk to go into open conflict, so the neutral zone is established, and no one gets the uranium. For the time being.