Van Zyl ran his first race of the season in Potchefstroom two weeks ago where he finished fourth in the 400m with a time of 46.50sec.
His coach, Hennie Kotze, indicated that the World Championships bronze medallist is hoping to qualify for the Olympics ahead of the South African championships next week.
Van Zyl, who will be running for Tuks, will have to run a time of 49.50sec to reach the Olympic qualifying A-standard time.
"We had a very good training session so we will see what happens on Thursday," said Kotze.
The South African 400m hurdles record holder's closest rivals in tomorrow's race will be Puks' Shaun van Wyk, and Bellville's Taariq Solomons.
Van Wyk ran a personal best at the South African junior champs in Germiston last week where he finished second in the under-23 men's 400m hurdles with a time of 51.34sec.
Van Zyl's other rival, Solomons, won the junior 400m hurdles title in Germiston in 51.49sec, narrowly missing out on the 51.46 world juniors qualifying time.