Constructing a regex to match attachments that have two or more specific labels is a bit more complicated. To do this, you must:

1. Set the Label match option to all.
2. Use a regex pattern similar to the following using xxx, yyy, and zzz as sample labels:

2 labels:  .*(?:.*\b(?:(?:xxx)|(?:yyy))\b.*){2}.*
3 labels:  .*(?:.*\b(?:(?:xxx)|(?:yyy)|(?:zzz))\b.*){3}.*