SM OU This is my first competitive team and i wanted to know what can I change.

[SarcasticBuccaneer]

Basically my team :
Alakazam (M) @ Alakazite
Ability: Magic Guard
Shiny: Yes
EVs: 4 Def / 252 SpA / 252 Spe
Modest Nature
IVs: 0 Atk
- Psychic
- Focus Blast
- Recover
- Shadow Ball

Keldeo @ Waterium Z
Ability: Justified
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Calm Mind
- Hydro Pump
- Secret Sword
- Taunt

Magearna @ Assault Vest
Ability: Soul-Heart
EVs: 248 HP / 224 SpD / 36 Spe
Sassy Nature
- Fleur Cannon
- Iron Head
- Hidden Power [Fire]
- Volt Switch

Landorus-Therian @ Leftovers
Ability: Intimidate
Shiny: Yes
EVs: 252 HP / 240 Def / 16 Spe
Impish Nature
- Stealth Rock
- Earthquake
- Hidden Power [Ice]
- U-turn

Greninja (F) @ Choice Scarf
Ability: Protean
Shiny: Yes
EVs: 176 Atk / 80 SpA / 252 Spe
Naive Nature
- Rock Slide
- U-turn
- Ice Beam
- Spikes

Tangrowth (F) @ Assault Vest
Ability: Regenerator
Shiny: Yes
EVs: 252 HP / 28 Def / 228 SpD
Sassy Nature
- Giga Drain
- Knock Off
- Hidden Power [Fire]
- Earthquake

Is this a good team?
I acept any suggestions to improve my team.

 

[Gross Sweep]

Welcome to Smogon! I'm locking your RMT for the time being as the forum rules require that you provide in-depth descriptions for each Pokemon to explain their roles. Please read the rules carefully and take a look at Team Showcase to see the level of detail we require. PM me with updated descriptions and I'll be happy to unlock this.