NK Dinamo Zagreb will defend a three-goal cushion in Baku next week after easing their way past Neftçi PFK with goals in either half.
Milan Badelj broke the deadlock eight minutes before the interval and two Ivan Krstanović goals, the second a penalty, put the Croatian champions firmly in charge of the tie.
Despite the scoreline there was little to choose between the sides in a quiet first half, but the home crowd were given something to cheer when the Dinamo captain pounced on a defensive error to score from close range.
If it took the hosts a while to get going before the break, the second half was only 15 seconds old when Šime Vrsaljko set up Krstanović with an inviting pass which the 28-year-old volleyed past Saša Stamenković.
Krstanović also won the penalty from which he scored his second goal, picking himself up after being felled by Stamenković to fire his spot kick beyond the keeper.