It is a very effective and very strong team, I have a similar team with 3 other Pokémon, Zapdos/Amoongus/Slowbro core is just too good, then have 2 Weathers can compensate for the weakness in the Sun's Team, but you are very disadvantaged against Gengar no? You can't kill because he outspeed Tyranitar, Hippowdon can do anything because gengar has Levitate and Hidden power Ice does not break the substitute, I suggest you put Tyranitar in Scarf, you can break the Substitute and coming to pursuit.
But I see that you are at a disadvantage against Volcarona, if it places a quiver Dance you can not do anything, I see also that you have lot of stall physical while in your team Slowbro/Forretress is widely enough, then I suggest you put on Dugtrio on Hippowdon, Dugtrio is a good counter for the Sun's team, because you're a little weak against this climate, and then he can come on Volcarona to the trapp and the kill with Stone edge, but I suggest you Dugtrio also because you can't do anything against Heatran, even with Slowbro because under sun it takes 50% on FireBlast (252 SpA Heatran Fire Blast vs. 252 HP / 0 SpD Slowbro in sun: 177-209 (44.92 - 53.04%) - 0.39% chance to 2HKO)
and heatran can be Toxic, Hippowdon can not come on heatran because it can be 2HKO or burn by Fire Blast / Lava Plume, now you can the trapp and the OHKO.
Also warning against Landorus Spec because it 2HKO Zapdos with Hidden power Ice if he is Sheer Force + Life orb, and amoonguss does not kill it with Hp Ice, Slowbro is OHKO after Steal Rock (252 + SpA Life Orb Sheer Force Landorus Earth Power vs. 252 HP / SpD Slowbro 0: 302-356 (76.64 - 90.35%) - guaranteed 2HKO)
Hope I Helped and Good Luck.