Map Optimization

My dad and I have been working on making a really big map of the world with level zero maps because they have an incredible 1-block resolution, and I ran into a problem. The displayed maps took up so much space in the world, that the world gave up, and started to crash every 15 seconds. The maps had made the world so large it reached 500 megabytes before dying. We restarted the project and discovered that just 128 maps took up 26 megabytes. And the sheer scale of 2000 maps killed it all. Some optimization would be greatly helpful even if just a tiny bit.