Hot shot Willett - signed from Hampshire Premier League outfit Paulsgrove in the summer - now has a whopping 36 goals in 41 games in his first season at this level after netting a hat-trick in the 4-0 win over the Isle of Wight side.
Meanwhile, striker partner Duffin took his tally for the campaign to 38 strikes in as many games - grabbing the other goal in the victory.
In the league alone, Duffin has netted 37 times while Willett is not far behind with 33 meaning the pair have provided 70 of the 109 goals the Deans have struck in 38 Wessex Premier matches.
‘The one good thing about all Zack's goals yesterday - sometimes he's very erratic in front of goal and he tries to take the back of the net off - all his goals yesterday we all very composed and he passed the ball into the net instead of trying to kill it.
‘He's just got to get that into his game because sometimes he's quite erratic and snatches at things.’
Things weren't as straightforward as the scoreline suggests in the early exchanges for the hosts, who had goalkeeper Cameron Scott to thanks for keeping things level with a couple of fine stops prior to Duffin heading the hosts ahead five minutes before the break.
Willett then got in on the act, with his tidy turn and finish on 63 minutes making it 2-0. His second soon followed, coming seven minutes later to make it 3-0, then the 19-minute hat-trick was complete with time running out to take fourth-placed Horndean to within two points of place-above Shaftesbury with two games left this season.