Ender Maps are "pre-zoomed".

When creating a map in the End, the "player-shaded" area of the map (in 128x128) is similar to a 256x256 zoom. This makes the zoomed maps more difficult to navigate as the shaded area gets smaller and smaller.

-128x128 map has a shaded-area similar to 256x256
-256x256 map has a shaded-area similar to 512x512
-512x512 map has a shaded-area similar to 1024x1024
-1024x1024 map has a shaded-area similar to 2048x2048
-2048x2048 map has a shaded-area similar to 4096x4096