Well, shoot, NOW I see this post.
The C-41 could be shot, overexposed 1-2 stops. One could try the same with the slide film and hope for the best, but E-6 is iffy with under/overexposure. Maybe 2-3 stops overexposed for cross-processing in C-41. It could be fun to try though.
Was the film refrigerated/frozen? Then it’d be worth shooting at box speed or eBaying.