There are those two similar projects:
Zepto is a minimalist JavaScript library for modern browsers with a largely jQuery-compatible API.
jQuery 2.0 beta: Here is your taste of the future, a jQuery that can be faster and smaller without the need to support IE 6, 7, or 8. It’s a great choice for platform-specific HTML applications.
Is this only about performance or do they follow different approaches?
The primary difference between Zepto.js and jQuery are their respective file sizes of Zepto.js's ~20kb (minified, not gzipped) instead of jQuery's ~80kb,And Zepto.js's ~10kb (minified, Gzipped) instead of jQuery's ~30kb. Furthermore, Zepto’s support for browsers such as IE<10 is either lacking or not guaranteed, its target platforms are: