Indeed, Mine Maze Zone is getting the chop. Castle Eggman Zone is getting all but nuked, bear in mind, so yes, the buttons of EXTREME HATE will be gone. Avid, uh 'fans' of CEZ may recognise one or two areas in the zones, but it's pretty much all change.
As some background information, Mine Maze Zone wasn't that bad a concept back in ye olde SRB2-TGF days, as I found a mechanism with which to make mine carts actually work, which could have made a nice gameplay addition; unfortunately, it's not particularly feasible to get them in SRB2, considering the payoff isn't that worth it for a barely controllable section of the game.
There is, however, no excuse for Rocky Mountain howevre; that was just my 13-year-old self going "HMMM YES THIS IS CLEARLY A WORTHWHILE USE OF A ZONE SLOT" and just slapping it in. RMZ was always going to be first on the list of doom, especially considering you have Red Volcano after it. Moreover, this meant three rock themed zones one after the over, which equates to a third of the game. I probably don't need to tell you that that makes for a game monumentally stale levels.
The other zones are probably going to remain as is, but there are no promises... ;D
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Johnny