Regional movies were never big threats no matter how big a hype they created. And it was Rohit Shetty who couldn't deliver to a level with Sanjay Leeks Bhanshali. SRK is always big, that's why Dilwale got the opening and overseas score. Aanand L Rai who knows the audience as he himself is a middle class like us can touch us, and Simmba with Rohit Shetty will be flying cars but will lose with visionary director's movie. Simmba and the lady-like muscular cop isn't a worry for SRK.
People here in this forum, specially SRK haters are posting all KGF, the forum is all KGF now more than Bollywood. Sarkar released back then with TOH but it couldn't stop TOH from being highest opener, so many of these came and went by and Bollywood movies always were the biggest. Even Bahubali couldn't stop a movie from being all time blockbuster because the Bollywood movie was good and not only because of Salman.
Aane do sab regional movies ko aur Simmba ko bhi, I would say, let them clash. Still, a good movie will earn.
I assure you, my dear brother, that Zero will be a very nice movie which even neutrals will like, and Sallu and Aamir fans praise.
So, basically, there is no stopping for this movie to be the highest grossing movie of the year at the least.