Even I have noticed it to be lower on Zebpay in the last week when there was sudden rise in BTC value. Maybe because Zebpay and others concentrate only on Indian market. But now it should be almost the same.
Avoid Zeb. There are better alternatives available. Buy rate at Zeb is always on higher side (uno being the king).
I just saw that rates on Zebpay is much better than that of Unocoin . At Zeb, I can buy currently at 389000 and on Unocoin after adding fees it comes to 398000. So now decide and tell which is better. Also Unocoin charges the highest fees as compared to any other exchanges in India.