We've been ordering from Zeal before my recent celiac diagnosis. Their online menu doesn't show many gluten-free variations, but when we called they we so great about it.
They confirmed that they offer GF (gluten-free) buns and their burger patties are also GF. You can get any burger option GF, except for the crispy onion strings.
They also have a dedicated fryer.
My GF order was in a separate bag with GF fries and clearly marked to avoid any cross-contamination with the rest of our family's order.
The service made me so happy and I'm even happier that I still get to enjoy Zeal. Thank you!