He was joined atop the leaderboard at The Country Club at Woodmore at 9- under-par 135 by Peter Tomasulo (67) and Patrick Sheehan (66).
Esteban Toledo, Paul Claxton and Livermore Valley Wine Country winner Omar Uresti share fourth place at minus-8.
Van Zyl got off to a rough start with a bogey on the par-4 second. He quickly atoned for that mistake as he ran off three straight birdies from the third to get to 4 under.
After a pair of pars, Van Zyl again ran off three straight birdies from the eighth to jump to 7 under. He parred the next five, then birdied two of the final three holes to grab a share of the lead.
'It was out there for the taking today,' stated Van Zyl. 'Up until last week, I've been playing nasty all year. But this golf course fit my eye quite nicely from the word, 'Go.''
Tomasulo had a solid front nine to climb the leaderboard. He collected birdies at the fourth and sixth to get to 6 under.
The 2005 Alberta Classic winner continued to make birdies every other hole as he birdied eight and 10 to get within one of the lead at minus-8.
Tomasulo gave a stroke back with a bogey on the par-4 16th. He closed with an eagle on the par-5 18th to gain a share of the lead.
'It was nice to make an eagle on the last hole and to leave on a good note,' Tomasulo commented. 'I'm excited for the weekend.'
Sheehan started on the back nine and was hot right from the start. He birdied four of five holes from the 11th to quickly get to 7 under.
The 37-year-old Sheehan parred seven in a row around the turn. He collected birdies at five and seven to get to nine-under before parring the final two holes to close out a bogey-free round.
Two-time winner this season Nick Flanagan, who tops the Nationwide Tour's money list, carded a two-under 70 and is tied for seventh. He was joined at 7-under-par 137 by Jon Mills, Jason Caron, James Driscoll, Kyle Thompson and Ryan Howison.
The cut line fell at 2-under-par 142 with 70 players moving on to the final two rounds.
Among those who missed the cut this year were four winners from earlier in the season -- Jacob's Creek Open winner Scott Sterling (143), Louisiana Open champ Skip Kendall (148), South Georgia Classic winner John Kimbell (146) and Athens Regional Foundation Classic Martin Laird (144).