At roughly 1,000-1,200 km depending on the city, Rajasthan from Mumbai is almost always a flying trip rather than a road one - Udaipur and Jaipur are both about 1.5-2 hours away by air, compared to a 14-16 hour drive that few operators actually offer as a package option.
An overnight train is the other realistic choice for travellers who prefer not to fly, typically running 16-18 hours depending on the destination city, and often used by those combining Rajasthan with a longer North India itinerary rather than a single quick trip.