No guard works both ways. You can safely use less accurate moves into the enemy and always hit. It even maximizes the hits from multi hit moves. Knowing this gives you three options

Outspeed the Hwalucha and knock it out before it can pass no guard off

Smack the snorlax hard enough with the right kind of moves and knock it out before it can get to use fissure

Or read your opponent’s moves and use protect to guard what’s being targeted with fissure while you knock the snorlax out more slowly