Techno

It was really tough for me as well. The thing about Garchomp is in the glitch field, it bases its special attack damage off of it's higher stat of SpA or SpD. And it has an assault vest. The way I won was using metal sound on Magneton with sturdy, so the Garchomp didn't one shot it. After that, the Garchomp did basically no damage. The tough part was dealing with the Hippowdon using Stealth Rock, luckily I crit it though.