I used your team on Showdown! a few times, and I can safely say, it's... not so great.
Your only reliable switch-in to ANYTHING is your Magnezone, and he's 4x weak to your main weakness.
Magnezone:
He's by far the best pokemon you have on your team right now. The Air Ballon is an ok item to use for him, but honestly, an assault vest would serve you better.
Golem-Alola:
Completely re-do this guy. You put max EVs into his speed. DON'T. he won't outspeed anything, even WITH the added EVs. Put those into Special Defense. Put all his Attack EVs into his health. He'd make a decent wall. Get rid either return or explosion. Some of my opponents tried to set up on me, you could also give Golem Focus Punch. Toxic is a good idea.
Tapu Koko:
The set you have is the Smogon set, but without the Choice Specs. Tapu Koko needs that extra power, especially since you fully invested in Speed. Plus, he won't last long anyway. Use him, then switch him out.
Zapdos:
Honestly, this role is already filled. I'd change him for Electivire, but if you keep him, re-do the stat distribution. You have him trying to sweep and be bulky, and you need to choose. It's fine to use the Smogon sets. In this case, I'd use the "Roost + 3 Attacks". He'd be able to switch into a predicted Earth Quake, and potentially sweep.
Rotom-Wash:
He's okay, and if you devote some more of your pokemon to a specific role, he is actually pretty decent at filling in any big gaps. Will-o-wisp is great, and he survived a few hits because of it. Pain Split can also be useful, it's really your choice.
Raichu-Alola:
I used Raichu a few times to sweep, and he did pretty well (even made a guy rage quit on me).His main problem is switching in.
He can't.
He can really only be brought in after Tapu Koko has set up Electric Terrain. Then he can sweep.
I suggest these changes:
Golem-Alola @ Lum Berry
Ability: Sturdy
EVs: 252 HP / 4 Def / 252 SpD
Sassy Nature
IVs: 0 Spe
- Toxic
- Stealth Rock
- Gyro Ball
- Explosion
Rotom-Wash @ Iapapa Berry
Ability: Levitate
EVs: 248 HP / 204 Def / 56 Spe
Bold Nature
IVs: 0 Atk
- Hydro Pump
- Volt Switch
- Pain Split
- Defog
Tapu Koko @ Choice Specs
Ability: Electric Surge
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
IVs: 0 Atk
- Volt Switch
- Thunderbolt
- Dazzling Gleam
- Hidden Power [Ice]
Raichu-Alola @ Life Orb
Ability: Surge Surfer
EVs: 252 SpA / 4 SpD / 252 Spe
Modest Nature
IVs: 0 Atk
- Thunderbolt
- Psychic
- Focus Blast
- Surf
Magnezone @ Assault Vest
Ability: Magnet Pull
EVs: 4 Def / 252 SpA / 252 Spe
Modest Nature
IVs: 0 Atk
- Flash Cannon
- Volt Switch
- Thunderbolt
- Hidden Power [Fire]
Electivire @ Assault Vest
Ability: Motor Drive
EVs: 4 HP / 252 Atk / 252 Def
Impish Nature
- Body Slam
- Brick Break
- Earthquake
- Power-Up Punch
I don't play Mono-Type very often, so if you get better advice, disregard this.
Anyways, that's what I got, Hope it helps!