I've worked on the project where some XSD files defined fields with regex restrictions, also some rules over fields added other stricter regexps or negative regexps depending on some context in a format called Schematron. I had to generate XML files conforming to those XSD, so I used some tools around Z3 solver and Microsoft.Automata to generate those strings conforming to multiple regexps. It would convert the regexps to finite automaton and intersecting them, walking it from the starting state to a final one over a charset.
Links :
https://www.microsoft.com/en-us/research/publication/symboli...
https://www.microsoft.com/en-us/download/details.aspx?id=523...
It now seems to be Open Source (MIT):
https://github.com/AutomataDotNet/Automata