Missing five key players, including top striker Alexandre Lacazette, Lyon on Wednesday claimed the convincing win employing a squad packed with homegrown footballers, reports Xinhua.
Maxwel Cornet tested Adrian Semper with a close-range flick after just 10 minutes into the match, before Corentin Tolisso struck, sending a powerful header into the net from Rafael's cross three minutes later.
Jordan Ferri made it 2-0 on 49 minutes after bursting forward to clip a delicious shot over Semper and into the far corner.
And eight minutes later, Cornet raced onto a measured Tolisso pass to prod home Lyon's third.
Zagreb struck the woodwork twice in the 61st and 87th minute, but Rachid Ghezzal would have given Lyon a plumper cushion had Semper not smartly parried his angled drive at 81.
Lyon, who lost all three home group-stage games last season, will go to Spain to face La Liga side Sevilla on September 27.
