I'm creating an extremely difficult challenge that combines multiple complex patterns:
1. IPv6 addresses (both full and compressed forms) with specific requirements
2. Complex time formats including timezone offsets
3. ISBN numbers with varying formats and valid checksums
4. Base64 encoded strings with specific patterns
5. Nested XML-style tags with matching names
6. Included similar "almost matching" items that should be excluded
This will require careful handling of:
- Multiple formats per pat... (truncated)