try using smogon for these movesets, these can be greatly improved with it
otherwise, time for me to improve this team based on my opinions
delphox:
run timid on it, delphox has an amazing speed tier at base 104, and max speed allows it to outspeed threats like landorus-t and the mega zards. as for moveset, replace hex with energy ball, and you could replace dgleam with trick as energy ball already covers tusk, although if you want to catch dragapult on the switch you could keep gleam.
other than that, great set!
garchomp:
run jolly. again, chomp has a great speed tier at 102, and this is more important considering the prevelance of mega zard y, allowing chomp to outspeed and stone edge it. as for moveset, i recommend choice band on it, as its high natural speed and great attack allows it dent a lot of mons on the spot. Another alternative is scale shot swords dance with rockium z for flying types, although there is a better sweeper down the line.
lucario:
t i m i d. max speed is crucial on tons of pokemon past base 80 speed, and lucario is no exception. outspeeding tusk in this meta is huge, and the rare specs glimmora is good to outspeed as well. modest is still viable tho as timid doesnt outspeed important other than those two.
as for moveset, i would say its decent. maybe a move can be replaced by vaccum wave for priority, but other than that i feel like this is solid
(this is coming from a person who has -1 experience using lucario)
magnezone:
zone is honestly hard to use in this meta. theres tusk, theres zard y, lando, heatran...
although...
with magnet pull, 252 hp 252 def 4 spa, bold nature, tera fighting, and a moveset of sub, body press, tbolt, and iron def, it is a great check to tera flying kingambit
mega gyarados:
ok. lets get right to the chase. d r a g o n d a n c e. replace dd over ice fang, you could have jolly or adamant idrk, and yeah.
tyrantrum:
honestly, i have no idea how to use this thing. the best advice i can give is to give it 252 speed, 252 attack, and 4 spd, then slot dragon dance over u turn and close combat over superpower.
hope you find this advice useful!