Simplification of regular expression
Minimizing a regular expression is PSPACE-hard, so there is no general method that is generally applicable and can be completed in a reasonable amount of time.  You'll need to inspect each individual situation on a case-by-case basis.

If you want to read about general methods, see https://cstheory.stackexchange.com/q/31630/5038 and https://cstheory.stackexchange.com/q/12361/5038.  CSTheory has a nice blog post with an overview of the field.  The alternative is to stare at that regular expression, understand very well what language it recognizes, and write down a shorter regexp.  You might be able to find some simplifications that work for that particular case, even though they are not general.