It's actually more of a Gayal/Gaur hump, much longer than that of a Zebu.
There is another hybrid animal in this herd that is very reminiscent of a Banteng.
Yeah, I'd say the hump was more Gayal-y. The head shape and the dewlap are Zebuish, though. The range of phenotypes in the 50/50 animals was pretty wide, and there are also (Gayal x Zebu) x Zebu animals in the herd as well (which pretty much just look like Zebus with slightly heavier horns).
Having had a second (and more importantly more sober) look I stand corrected. The zebu hump that I referred to is not as large and pronounced as I thought it was last night with the beer goggles on!
Thanks all for the correction.