Rate my X team

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Xerneas. Item is kings rock.
Geomancy
Moonblast
Megahorn
Thunderwave

Gogoat. Item is meadow plate.
Bulk up
Leaf blade
Synthesis
Earthquake

Tyranitar. Holding a tyranitarite.
Crunch
Stone edge
Surf
Earthquake

Tyrantrum. Holding a dragon fang.
Crunch
Draco meteor
Earthquake
Head smash

Zapdos. Holding a zap plate.
Thunderwave
Thunderbolt
Drill peck
Agility

Snorlax. Holding a rocky helmet.
Belly drum
Giga impact
Rest
Substitute

Any help would be great as I have yet to test this team online..

[Zak Rodgers]

Xerneas: Interesting. Paralyzing your opponents with a chance to make them flinch on every strike makes this a good stall Pokemon. However, Xerneas's gifts lie in tying its high offense and its Geomancy move together.
3/5

Gogoat: I really like this one. Defense buff + healing + attack buff + powerful moves make this one a real powerhouse. Good type coverage too, except for flying-types. Gogoat is also a little slow.
4/5

Tyranitar: Standard offensive threat here. Consider Rock Polish, Spikes or Stealth Rock - Tyranitar's speed leaves a little to be desired, and with its high stats, both offensive and defensive, it can last long enough to set up multiple entry hazards while tanking most hits and dealing great damage of its own.
2/5

Tyrantrum: Lose Draco Meteor. Tyrantrum is a physical attacker before anything else so get Outrage or Dragon Rush. This would make the dragon fang unnecessary; so if you do get Dragon Rush give it a King's Rock: you'll get a great flinch chance. Also consider Bulldoze, because (as is the case with most of your Pokemon) Tyrantrum isn't the fastest. Even with Bulldoze's average power, Tyrantrum's high attack stat will make it hit decently hard while lowering your opponent's speed.
1/5

Zapdos: If Drill Peck's working for you, keep it. I've always used Zapdos as more of a special attacker so consider Air Slash instead. It takes advantage of the high special attack stat and can also make the target flinch. I like the Thunderwave/Agility thing. While they're unable to move, you can boost your speed through the roof. I honestly can't find a lot wrong with this one, but maybe EV train for defense/special defense and beware of Stealth Rock.
5/5

Snorlax: If you play your cards right, this can become an immovable tank. After Belly Drumming, use Rest. Replace your rocky helmet with a Chesto or Lum Berry - you'll wake up immediately with full HP and a maximised attack stat. Be careful with this however, as in the short window where Snorlax is at 1/2 HP it's vulnerable. While Giga Impact coupled with the maximized attack from Belly Drum is nearly unstoppable, the next turn is wasted and your opponent is free to pummel on you. This can affect your timing for Rest and ultimately cost you the fight. Substitute is unnecessary because of the Rest strategy. You'll just end up wasting HP. Replace it with Sleep Talk (the strategy of using a Chesto/Lum Berry to wake up straight away only works once per battle unless you have a trick up your sleeve) so you can still use moves while asleep. Be careful though, because if you try to use it on the turn Snorlax wakes up, it'll fail and you'll waste a turn. Overall, there is plenty of room for error with this one - you can waste turns very easily and with Snorlax's low speed, it'll take damage quite often, forcing you to spam Rest. I don't recommend using this one competitively, but you can try. Opponents generally come up with too many counters for poor old Snorlax.
0/5

Overall, you have a good team, but almost all of them are fairly slow. If you do choose to battle with these six, I recommend you take the advice I've given as well as super-training for defensive stats and speed stats. Remember online players know lots of ways to do hideous damage quickly, so focus on taking as little as possible. Good luck, and hope I helped! Also, sorry if this posts twice - I have no idea why it happens.

[Zak Rodgers]

Xerneas: Interesting. Paralyzing your opponents with a chance to make them flinch on every strike makes this a good stall Pokemon. However, Xerneas's gifts lie in tying its high offense and its Geomancy move together.
3/5

Gogoat: I really like this one. Defense buff + healing + attack buff + powerful moves make this one a real powerhouse. Good type coverage too, except for flying-types. Gogoat is also a little slow.
4/5

Tyranitar: Standard offensive threat here. Consider Rock Polish, Spikes or Stealth Rock - Tyranitar's speed leaves a little to be desired, and with its high stats, both offensive and defensive, it can last long enough to set up multiple entry hazards while tanking most hits and dealing great damage of its own.
2/5

Tyrantrum: Lose Draco Meteor. Tyrantrum is a physical attacker before anything else so get Outrage or Dragon Rush. This would make the dragon fang unnecessary; so if you do get Dragon Rush give it a King's Rock: you'll get a great flinch chance. Also consider Bulldoze, because (as is the case with most of your Pokemon) Tyrantrum isn't the fastest. Even with Bulldoze's average power, Tyrantrum's high attack stat will make it hit decently hard while lowering your opponent's speed.
1/5

Zapdos: If Drill Peck's working for you, keep it. I've always used Zapdos as more of a special attacker so consider Air Slash instead. It takes advantage of the high special attack stat and can also make the target flinch. I like the Thunderwave/Agility thing. While they're unable to move, you can boost your speed through the roof. I honestly can't find a lot wrong with this one, but maybe EV train for defense/special defense and beware of Stealth Rock.
5/5

Snorlax: If you play your cards right, this can become an immovable tank. After Belly Drumming, use Rest. Replace your rocky helmet with a Chesto or Lum Berry - you'll wake up immediately with full HP and a maximised attack stat. Be careful with this however, as in the short window where Snorlax is at 1/2 HP it's vulnerable. While Giga Impact coupled with the maximized attack from Belly Drum is nearly unstoppable, the next turn is wasted and your opponent is free to pummel on you. This can affect your timing for Rest and ultimately cost you the fight. Substitute is unnecessary because of the Rest strategy. You'll just end up wasting HP. Replace it with Sleep Talk (the strategy of using a Chesto/Lum Berry to wake up straight away only works once per battle unless you have a trick up your sleeve) so you can still use moves while asleep. Be careful though, because if you try to use it on the turn Snorlax wakes up, it'll fail and you'll waste a turn. Overall, there is plenty of room for error with this one - you can waste turns very easily and with Snorlax's low speed, it'll take damage quite often, forcing you to spam Rest. I don't recommend using this one competitively, but you can try. Opponents generally come up with too many counters for poor old Snorlax.
0/5

Overall, you have a good team, but almost all of them are fairly slow. If you do choose to battle with these six, I recommend you take the advice I've given as well as super-training for defensive stats and speed stats. Remember online players know lots of ways to do hideous damage quickly, so focus on taking as little as possible. Good luck, and hope I helped! Also, sorry if this posts twice - I have no idea why it happens.

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The advice is good, but mamoswine is common and heatran would give me trouble. Thanks!