mip mapping,- way to cache lower resolution images of the texture and use it at different distances. WHen the original images gets to blurry switch it with a new one that offers a better detail for that zoom state.

Though if I were you i´d check out some simple FOV (field of View) examples that scale sprite, graphics or cars depending on their distance towards the camera. Search either here on the board, flashkit.com or google to find information regarding those