The only vehicles allowed to come in to a Free Zone company as "duty-free" are those with seating for 12 or more , and are considered as employee transportation. That doesn't include a vehicle for the use of the owner or anyone else (sorry).
However, a Free Zone company does not have to pay the 16% ITBIS on a vehicle purchased here in the DR, and that is a great discount. Just don't tell the dealer that fact beforehand, but after you have agreed on a price, INCLUDING taxes.