Zaxara is better than you think (EDH / Commander)

First, english isn't my native language so I apologize for all mistakes I will make.

The plan is easy : Turn 1 / Turn 2 Ramp with all ramp spells you can. The goal of the deck is to put Zaxara in play Turn 3.

If you cannot ramp during these turn you can also set up the game with Rhystic Study or Elemental Bond for card draw, but also selvala and chromatic lantern to ramp later and fix your mana.

After that you just need to use your X spells at the good time to draw cards or counter your opponent. I think that you shoudn't become full tap during your main phase, even if this is for ramp, always keep 3/4 mana if able ( except for seedborn muse which is God Tier ).

When this is a good moment ( counterspells in the hand or your opponents are full tap) you can use the tutors to find your kill if you have many hydras. Or your X kills if you have many hydras. If you have a X kill in hand who can finish the game or a X draw spell or another tutor in hand you will search for Freed from the Real or Pemmin's Aura to do infinite mana and close the game. But always remember that this isn't the only way to win.

Ramp : Arcane Signet, farseek, nature's lore, rampant growth, sakura-tribe Elder : T2 ramp for a T3 Zaxara.
Birds of Paradise, Elves of Deep Shadow, sol ring, mana crypt : T1 ramp because their is nothing better than that and we have some 3CCM spells worth to play T2 or just a X counterspell for X=2 become really effective.
Selvala, Heart of the Wilds : Big Ramp + Fixing + CA = god tier
Nyxbloom ancient, Mana Reflection : So powerful, nyxbloom ancient is easy to search
Thran Dynamo, Gilded Lotus : Always Good to have
Animist's Awakening : X spell + Ramp for bigger X spell ( spell mastery is easy to trigger ) perfect

Freed from the Real and Pemmin's Aura : Infinite Combo ( + shroud ) perfect

X kill : Exsanguinate, Torment of Hailfire and Walking Ballista are game finishers. Profane Command Can Kill someone, the fear can kill another opponent and the other mods are always good in many situations

kill : Craterhoof Behemoth : OOF
Triumph of the Hordes: Easy to kill everyone with some 15/15 put during the opponent turns

Draw X : BSZ, Pull From Tomorrow, Stroke of Genius, Epiphany at the drwnyard : Instant Speed, Draw X ( or find half of the good cards in the top X ) just what we need
Finale of Revelation, Gadwick, the Wizened : Sorcery speed but interseting drawback especially for the finale.
Hydroid Krasis : Good Body ( which can be a kill ) plus a good draw and some lifegain, strictly better than gadwick, the Wizened
Villainous Wealth : Just for the fun i apologize :)

CA : Rhystic Study : Nothing to say
Elemental Bond : Easy One or Two more cards per turns table, for 3 mana it's ok

Counterspell X : Condescend, logic knot, power sink, syncopate : Clash of Wills with advantages
Thassa's Intervention : Clash of wills or " dig through time" with X cards instead of seven
Spell Burst : This card is just incredible with seedborn muse and good alone

Counterspell : Mana Drain, Spell Swindle : Thanks you for you mana, that will make a bigger hydra.

Gestion X : Black Sun's Zenith : Just because this is extremely powerful not for the X
Curse of the Swine : Exile + many targets + X , this is perfect. They have boar we have Hydras.
Erebos's Intervention : Kill through indestructible + X + Life gain or exile graveyard if needed, cool !
Icy Blast : This can protect us against big board, and can just remove blockers for the win

Gestion : Assassin's Trophy, Maelstrom Pulse, Beast Within : No target restriction
Toxic Deluge : Best Wrath of the game ( at least in black )
Cyclonic Rift : Best "wrath" of the game ( at least in blue )

X tutor : Chord of Calling : Instant speed + convoke + put in on the board perfect ( selvala or nyxbloom at instant speed ; Craterhoof for the win )
Finale of Devastation : Double OOF let's go

Tutor : They are all cheap and can search for anything.

X Good Stuff : Dominate, Entrancing Melody, Mass Manipulation : Why kill this powerful permanent when you can just take it ? Instant speed for dominate and mass targets for mass manipulation
Wildest Dreams : Best card to reuse all good cards in our gy absolutely perfect

Utility Lands : Classic utility land package

The deck is between 7 & 8 ( I would say 7,5 and it depends a bit of the meta of your playgroup ). If you want to make it better, I think that you could change big mana ramp and maybe some X counterspells ( depends on your need of blockers ), even maybe all the craterhoof like kills and focus the deck on searching for your combo and control the game with cheapest counterspells ( Force of Will, force of negation, pact of negation, fierce guardianship, etc ... ) and add more control cards. I don't do it because this is not how I want to play with this commander but I could understand that some people want to push him at his higher potential, feel free to do as you want !