Axelyx

Houndstone

Teach bounce to dragalge from the tutor in akuwa, bounce can change the field into sky field. This can reduce the field boost for typhlosion and remove passive eruption damage. Also, I believe electabuzz, talonflame and yanmega can benefit from sky field boost. Once sky field is up, I recommend using elemental seed to set up tailwind if you have it. And if scrafty has intimidate, you can try switching him in and out to lower the enemy’s attack. Also remember to max your mons levels for the highest damage :)

Iron moth

Abomasnow

Arboliva

Espathra

Tympole

Nacli

Well there’s no in-game ‘legal’ way, but you can change it using the debug mod. Just go to the mod market and look it up.

Noivern

Koraidon

Trumbeak

Ralts

Ursaring

oranguru

fuecoco

Rockruff

Yamper

Smoliv

Yveltal

Entei

Which z-crystal to be exact? If you mean the z-ring (that allows you to use z-moves if a mon is holding a z-crystal), it’s obtainable after the 13th badge. More on this here.

Xurkitree

Naganadel

Umbreon