I don't know the history for this tree, and only the owner could provide you with that. In all likely hood, the tree was grown from a young cutting or seed, as are many tropicals in Taiwan. It may have started it's bonsai training a human generation ago or more. The weather in that part of the world allow this species of tree to grow year round in perfect conditions. The beautiful nebari (rrot crown) that you mention will have been achieved through years of cultivation and work, and year living in shallow bonsai pots. It is most possible to grow a tropical bonsai like this in zone 7, but you will need to work in an environment that is not suitable year round for tropicals. That would mean it will spend part of it's time indoors in a green house, or special grown room with proper lights and humidity. Jerry Meislik, who live in Montanna is a specialist in this regard (
http://www.bonsaihunk.8m.com/ ). That said, you will need to sart with excellent material to begin with, to achieve something as impressive as what you show here. Your local club may be able to help you with this effort when you are ready. Good Luck!