De Guzman claimed a treble as Napoli moved a step closer to qualifying for the UEFA Europa League's knockout phase at the Stadio San Paolo.
The Dutchman broke the deadlock in the second minute of first-half stoppage time, before completing the scoring in the 65th and 83rd minute
"We played well and deserved the victory," De Guzman told Sport Mediaset.
"I am very happy with the goals, but we must continue to work hard.
"We played well in the last few games and that is very important for us."
Napoli manager Rafael Benitez, who oversaw the Serie A team's fourth game without defeat in all competitions, refused to single out De Guzman.
The Spaniard, instead, opted to praise the team as a whole against the Swiss visitors as they moved level on nine points with Group I leaders Sparta Prague.
"It is difficult to talk about just one player, as there was a great collective performance this evening," Benitez said.
"It was important to score three goals and not concede for the goal difference, so we could avoid what happened last season.
"Rafael therefore did very well on that last chance, but there were many positives tonight. It was a great performance despite the various changes."
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