THEY ARE REALLY ****ING HARD I REMEMbER THE FARTHEST I GOT WAS LIKE THE FORTH GYM IN A SINGLE POKEMON NUZLOCKE THATS IT. legit they are so hard but so fun to do but it will kill you in the inside if you lose a pokemon your deeply connected to
If there's a route with a high change of encountering sneasel I think you'll be alright, weavile can outspeed garchomp I think and hit it eith a 4X super effective ice move