Leeds skipper Wentzel ran in two of his side's eight tries at Headingley
Leeds romped to only their second win of the season as they maintained their chances of qualifying for the knockout stages of the European Challenge Cup.
Tries by skipper Marco Wentzel and Lee Blackett earned Neil Back's men a 15-6 half-time lead at Headingley.
They then added six more tries after the break, winger Blackett and lock Wentzel both adding a second.
There were also tries for full-back Ceiron Thomas, Peter Wackett, Leigh Hinton and Henry Fa'aifi.
The only response from Parma came by way of two first-half Tommaso Iannone penalties.
Thomas kicked a penalty and three conversions before going off, after which Hinton came on to land three out of three conversions.
It was a first victory for Leeds, who have lost all their nine games in the Premiership, since their only other win this season - also in the European Challenge Cup, 23-9 in Bucharest on 9 October.
Leeds, who had not won at Headingley since the day won promotion in April, now face the return leg in Parma next Sunday (1330 GMT).
That is then followed by the crucial trip to Pool 4 leaders Stade Francais on 15 January and the final group game a week later at home to Bucuresti.
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