What Sean said. You cannot infinitely zoom into a 2D picture.
There are two general solutions animators use.
1) create several ‘worlds’ at differing proximities and wipe between them (easiest)
You create, say, 3 views of your planet: one from space down to about atmospheric level. Make a satellite cross your line of view, and use that as a cut point to your next, closer resolution image. Then wipe with a plane or cloud to your next closest resolution image, etc, etc.
2) create several ‘worlds’ at differing proximities and dissolve/morph between them (most awesome)
This is a bit like the way Google Earth works, and is way more painstaking. Start from space view, and get as close as you think you can to your planet without getting too blurry (tip: fill the frame with the planet). Then render that final image out, enlarge it in Photoshop or GIMP (whatever), and then re-create the scene by drawing in more detail. Once done, wrap it to a plane and track into that.
Now you have two separate pieces of footage, one ending where roughly the other begins. Bring them into an editing program and dissolve/morph between the two at the transition point.
The movie ‘Gravity’ is an amazingly rich, visual spectacle. It features a planetary model of Earth that would melt any 5 modern, domestic computers to render out and composite. And you never track into it. It’s all cut to different views.