Just months after buying a six-building Jamaica portfolio, Zara Realty made another multifamily purchase in Queens — a 76-unit rental building in Elmhurst. The southeast Queens landlord paid $21.1 million for the place at 51-25 Van Kleeck Street, according to property records filed with the city Tuesday. The building has six stories and spans 65,000 square feet. Out of the 76 apartments, 51 of the units are rent-stabilized, according to Reonomy.