Ok mega Camerupt is not as reliant as Zard-Y on sun. In rain, Zard-Y is deadweight because Fire Blast is weak and Solarbeam can't charge. It has to rely on Focus Blast for coverage, and yes, having to use a 70% accurate move is not a good thing. Zard-Y is SR weak, and also Camerupt is SR neutral. Speaking of which, Camerupt can set up SR on switches. Plus Camerupt has ground STAB, something Zard wishes it got. Flying typing is useless offensively for Zard as Air Slash is shit. You are forced to run Roost over coverage like Dragon Pulse so you can actually switch in on SR. Defog support is mandatory for Zard Y at all times. Camerupt can run Fire Blast and Earth Power, and usually Ancient Power, and the last one or two moveslots are free. SR, Wisp, Toxic, etc are all good choices. Zard Y and Camerupt aren't the same thing, they have different roles. But if you say "Just use M Charizard" lets see who they hit.
Zard Y hits harder on non-resists with Fire Blast. However must mons are nuked anyway by Fire Blast from both. However, Zard Y is fodder for mega Mence(!), Dnite, Charizard X, and can't hurt Politoed in rain. On the other hand Camerupt can hit all of those hard by running Ancient Power, and if isn't, then it can burn them. Camerupt has two STABS to work with, Zard Y only has one, although this one does hit harder. Sure mega Camerupt also can't really hurt Lati twins and its slow, but that's what team mates are for. I'm not saying on is better than the other, I'm just saying they have very different jobs.
LO Heatran has worse STABS, wears itself down with LO and still doesn't hit nearly as hard. Keldeo is faster, but its STABS are resisted by a lot more than Camerupt, and has a much worse case of 4MSS, not to mention it is choice locked, which is especially dangerous with stuff like Mence flying around. Finally don't even try to compare mega Camel to Gunk Ninja its just broken, this thing was S before it got Gunk Shot AND Low Kick RIP AV Azu. You have to admit that Greninja is a better mon than Zard Y as well.
Edit wow sniped, yeah I forgot to mention it shuts down every user of Volt Switch in OU besides Rotom-W and Lanturn(yea it can't switch in on Earth power tho but all other volt switchers can't do anything even with a free switch(pun intended)) The point is Zard Y and Camerupt are very different mons, Zard definitely doesn't outclass Camerupt.