Okay, it's been awhile since I've watched Zeo, but here's my suggestion.
When you ask how Tanya has a family, do you mean how she has a family after the rangers are restored to their original ages? If so,
www.tvtome.com's review of Hogday Afternoon Part 2 (MMPR) states that since Tanya returns instead of Aiesha with the zeo crystal that alters the timeline and Tanya's parents will be with her when time returns to normal.
As for the whole Mondo/Zedd/Rita ordeal, the gift that Zedd and Rita gave Prince Sprocket exploded and they just rode off. It's not known whether or not they took over the Machine Empire, but in the final episode of Power Rangers In Space (where Andros shatters Zordon's energy tube, eliminating all evil at the time) the Machine Empire is defeated along with the other evil in he world.
Bottom line, there's nothing telling what happened to the empire between Zeo and In Space.