This is version 2.0 of Zem80. It is a complete redesign of the emulator core with the goals of having a cleaner architecture, more modularity, better timing and porting to .NET 8.0.
Some minor breaking changes were introduced to the API and events, but these will be obvious from context. Update your project to .NET 8.0 and build and see if any errors pop up.
Full Changelog: 1.2.2...2.0 - warning, this is a HUGE set of changes!