This looks like a fun team, but it's pretty weak to numerous special breakers and sweepers. D_A mentioned Greninja, but you're also in real trouble if Keldeo comes in for a revenge kill or on your own Keldeo. You have plenty of revenge killing for it, but it's still going to do its job. Charizard-Y can come in early game on Clefable and is pretty much guaranteed a kill. Mega Gardevoir has a ton of opportunities to get in, and you don't have a Fairy resist to take Hyper Voice. So I'd pin that as the team's major problem.
Otherwise, the two notable weaknesses I see are Sand Rush Excadrill and Mamoswine. Sand is definitely a weak but one a team like this has to play around, and I think you're equipped to do so reasonably well. Mamoswine, on the other hand, is just a terror, and every time it comes in to revenge kill you get to decide whether to risk Keldeo or not. I think that weakness is pretty natural with four Ice weaks, haha.
I think the misfit here is Zapdos. It's a bit of a momentum killer that is only compounding the weaknesses of a triple-Flying core in Land/Thund/Pinsir. BirdSpam is really strong and countering it is nice, but I just don't see its purpose.
I agree with D_A's suggestion of HP Fly on Thund, as Mega Venusaur actually walls this team pretty badly except Pinsir (which sucks because it forces predictable play that your opponent can exploit), and luring it in is hugely useful. CC>EQ on Pinsir is also a good suggestions. I would also consider Superpower on Landorus-T since M-Gyarados and M-Tar can't really be overprepared for, it it helps with Balloon Exca. Whether you want to lose Knock Off is another story though.
But yeah, to fix the weaks outlined above, I think Zapdos has to go. The more extreme solution would be running Scarf Spin Exca over Land-T so you can use something in the Zapdos slot besides
[email protected] [email protected] fits nicely over Zapdos but compounds weaknesses to Gardevoir, Greninja, and Mamoswine, though it does help a lot with M-Venu, Keld, and Char-Y. (I'm also cautious to get into super-standard core territory with Keld/Thund/
[email protected]) So my suggestion is going to be running Starmie over Zapdos, presumably with a moveset of STAB/Thunderbolt/Psyshock/Rapid Spin? (I actually don't know what Starmie runs lol.) Anyway, Starmie can also benefit from the removal of M-Venu or just do that itself. It removes SR while keeping your own, forces out troublesome special breakers (except Gard, but you're just going to have to live with this weakness) and Mamoswine.
Anyway, I dig the Pinsir/Thund/Keld set-up--they are three of the best OU mons--and I can see this being a fun team to play with. Good luck with your team br0.