An upbeat Heyns, riding for Team DSV, was just too strong for his competitors, crossing the line in two hours, 53 minutes and 10 seconds.
He claimed the chequered flag ahead of Durban's Andrew Hill (2.53:46) and Nicol Carstens (2.53:48) from Worcester.
Speaking after the race, Stellenbosch-based Heyns said: "I'm feeling good, it was a nice race, and I'm glad with the result. I went quite hard, in the beginning, to try and get away on the single track.
"The route was really fun, I managed to open up a gap going up through the pass, but towards the end they were chasing me all the way. But, I managed to hold out [for the win]."
In the women's section, Oudtshoorn's De Villiers, riding for Team Silverback Volvo Racing, put up a commanding performance on the course, racing to victory in a time of 3:10:27.
De Villiers finished almost 20 minutes ahead of her nearest competitor, Bay rider Anriette Schoeman who finished in a time of 3.29:40. Another PE rider Siska van der Bijl was a further three minutes behind in 3.32:12 in third.
De Villiers said: "This whole area is so fantastic for mountain biking, conditions were near perfect out there."
De Villiers and Heyns were named king and queen of the mountain for being the first riders to make their way up the Zuurberg Pass
In other results, top three finishers per race distance were:
60km men, Gerrit Rautenbach (2.16:25); Raye Moolman (2.19:05) and Matthew Spanjaard (2.21:07)
60km women, Gail Willimott (2.44:47); Michelle Scowby (2.51:31) and Beth Marais (2.55:52)
30km men: Partridge Chimwendu (1.03:56), Benjamin Brown (1.03:57) and Marcell Swartz (1.03:58)
30km women: Ashleigh Mayhead (1.05:59); Ancherien du Plessis (1.11:21) and Elize Strydom (1.11:24)