There’s a good FastTalk podcast on two a days. Seems to suggest the workout first and then a Z2 etc ride later on. I don’t think you need TN for that second ride. Try to keep the gap as short as you can given you presumably have a full work day in between - I don’t remember exactly their recommended gap but I think the ideal gap was 5hrs or something.
Apparently this is a really good way to get some/many of the benefits of doing a long ride, without doing the long ride…