Well I don't know about Zero. Since as far as I know it was exclusively for Nintendo machines. Nothing can change that (If it's true I mean) but looking at other resident evil games we see that RE2 and 3 were ported for GC but with the same old graphics (Just a direct port, not like RE1 remake). So another porting for PS2 wouldn't be hard specially that RE games returned once again to PS2 with RE4 and RE Online.
But still that depends if they think it'll give money for them. Maybe if they port RE gun survivor it'llgive more money than RE2.0 (ofcourse that's impossible but it's an example
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