The Scot netted twice early to establish Blues dominance, while the Brazilian ran the show from midfield as the hosts overran their Norwegian opponents after the break
Feruz netted twice in the first half to help the Blues assert their dominance early on against the Norwegians, while Piazon weighed in with two assists and a superb free-kick as the hosts ran riot.
The result leaves Chelsea third in Group 3, two points behind last season’s finalists Ajax, with two crucial contests against the Dutch giants still to come.
The Blues enjoyed the better of a lively opening spell, and might have taken the lead inside a minute when Piazon squared the ball to Lewis Baker, who fired wide.
Molde rallied, and three minutes later wasted a golden chance of their own when a neat pass from Andreas Hollinngen set Jan Aboubacar bearing down on goal, but his tame effort was easily saved.
They were quickly made to pay for their profligacy, as on nine minutes Piazon cleverly slid through Feruz, who nodded into an empty net having seen his initial shot well saved.
Chelsea’s main threat was coming through the positive runs of left-back Adam Nditi, and on 17 minutes a surging run and powerful shot forced Sivert Beinset into a decent save.
But the hosts’ neat interplay made another breakthrough inevitable, and on 22 minutes Nditi rampaged forward again and crossed low for Feruz to tap in his second.
Chelsea were in complete control but appeared content to stroke the ball around rather than go in for the kill, and a two-goal lead at half time did not adequately reflect their dominance.
After the break they stepped up a gear, however, and four minutes into the second period substitute Piazon meet substitute Alex Kiwomya’s precise low cross with a strike which crashed off the post.
The Blues kept probing but were forced to wait until the hour to extend their lead, Kiwomya finishing a sweeping move by turning swiftly and driving the ball low into the bottom corner.
Conceding a third appeared to beat the last of the resistance out of Molde and, in the last half hour, Chelsea ran riot with Piazon at the heart of much of their good work.
On 69 minutes, the Brazilian showed great awareness on the edge of the box to find Reece Mitchell, and the substitute promptly turned his man before curling beyond the helpless Beinset.
The visitors no longer appeared capable of withstanding any sustained pressure, and three minutes later Piazon expertly swerved a free-kick into the corner after Isak Ssewankambo had been fouled on the edge of the box.
Insult well and truly added to injury, Chelsea could have been forgiven for settling for just the five goals, but with 15 minutes left Mitchell sent a hanging cross to the back post, where it was met with an emphatic volley by skipper George Saville into the bottom corner.
The final quarter of an hour was seen out in comfort by the Blues, while the final whistle was greeted with relief by the dejected visitors.
Ajax will pose a considerably tougher test, but Chelsea will travel to Amsterdam at the end of the month with qualification still very much a possibility.