I'm designing an extremely difficult regex challenge that combines multiple advanced pattern types:
1. Nested JSON objects with escaped quotes and unicode
2. IPv6 addresses with compressed sections and mixed formats
3. Complex nested XML with CDATA sections
4. Mathematical expressions with superscripts/subscripts
5. CSS selectors with complex pseudo-classes
6. Custom format timestamps with microsecond precision
7. Unicode domain names in URLs with complex query parameters
8. Quoted strings with ... (truncated)