Well your spinning cube uses very little vertices and transformations, so it is probably fill-rate limited. Zooming in on the cube means drawing more pixels and thus using more of your fill-rate. The only way to speed it up AFAIK is buying a better videocard or not drawing as many pixels.

However you can make the cube spin at the same speed no matter how many pixels are drawn. You''ll need to use a timer of some sort like timeGetTime or something similar. What you do, is measure how much time elapsed since last frame. (let''s call it delta_time) Now instead of this piece of C/C++ code:
rotation_angle += rotation_speed;
You use this:
rotation_angle += rotation_speed*delta_time;
This way the cube will always rotate at the same speed, regardless of how many frames are rendered per second.

Dirk =[Scarab]= Gerrits