I dont have much experience with M2M, but I've noticed my opponents shooting % is usually lower than my conference counterparts who primarily run man and press.
As far as how to handle slasher guards, its still like the other defenses where your personnel will determine a lot, but you could always run a 3-2 and sag it in. It's hard to compare results because there are not many people who run zone and run it successfully, but theoretically if you sag it, I assume if they are slashing, your bigs will pick them up inside, and your guards will cover mid range shots better, but your defense against the 3 will be less effective than a 3-2 at 0 or -1. This is HD though, so theoretically might not work here.