Zylach
I'll try
Low % (0-30) Lucario:
Zelda is a relatively difficult matchup for Lucario in the sense that one of Zelda's main tools in neutral and for gtfo either come out faster (things like d-tilt, d-smash, sh nair, grab) or are intangible/reflect (nayru's love) than Lucario's neutral tools. In this matchup, Lucario is also forced to approach Zelda in sheild due to reflection, but Lucario's approach options consist of cute footsies like empty hope, b-reverse or wavebounce Aura Sphere, shff nair, fair bait>dair/nair/aurasphere charge or simple dash footsies into grabs or dash attacks.
Zelda either beats these or outranges them with nayru's love if the Lucario chooses to go aggressively into Zelda with these options except for maybe fair>dair/aura sphere charge, in which case, it's best to fully sheild those or fox trot backwards and outspace these options, losing some positioning, but retaining your life. Keep in mind, I am talking about low percent lucario. Often times, holding shield at these low percents and waiting to see what lucario is going to do, especially if he's short hop happy is good and valuable for Zelda. A pure ground lucario who likes using fox trot and grounded b-reverse aura spheres is a bit more tricky here considering how shield pressure changed. If this is happening, Zelda can try to run away djinns (pretty bad), predict Lucario's movement and hit it with an f-tilt, d-tilt, f-smash, up-b, anything that can either suddenly appear or out space Lucario, or hold shield. At these percents, being grabbed by Lucario isn't too bad for Zelda as he can't nair>re-grab due to your floatyness, so he can either fair>fair> or upair.
Medium % (30-70) Lucario:
You can treat this like low % Lucario, but with less combo game possible. Reversed Aura spheres are a big problem here from neutral still, but by now, Lucario won't be able to fair combo as easily and it works to just get some meager %. In these percents you can still d-throw> DI read nair or up air, which if hitting around 60-70, is very dangerous for Lucario. Unless you're around 90%, Lucario shouldn't be able to kill you with force palm yet.
Saiyan (70+%)
Normally Mega Lucario is a problem for a lot of characters, but because Nayru's love is intangible during force palm, grab, and reflects Aura sphere, it's not as bad for Zelda as other characters. Her weight and floatinyess make up throw> up air, hard to land if you are equal in percent. This is the point where Lucario is going to be hard baiting you for those gtfo options with either shield or dash, or b-reverse movements. If you used nayru's love early on for gtfo, be prepared to change your game, because it can and will be forcepalmed if he dash shields into you and you will die. If you were afraid of up-throw>up air, and tried to air dodge, back air reads on the air-dodge will kill you. Zelda's saving grace at these percents are that her d-throw combos are now air dodge traps. It's pretty much like Sheik, where you must jump or the up>air will hit. Zylach has killed me in this range before. Also, be wary of Lucario's counter as it scales with aura, not damage dealt/knockback. It starts killing around here.
Off Stage
RIP Lucario. We like shooting aura spheres or force palms to get you off guarding the ledge, but you have Love powers spinning around to protect you. If Lucario is recovering low, Jump, wait, dair. Even the weak hit, puts lucario in the positiong to recover low again and Luca has this weird thing where if he's too far from the edge during ExtremeSpeed, he literally won't grab it. It doesn'thappen from below often, but if you're threating the straight up option, he may have to back off. Horizontal recovery is easy to stuff with nair, or if you're brave, dair, bair or fair. Extremespeed's hitbox comes after Lucario's body, so don't be afraid as long as you're throwing a hitbox out there. As for what Lucario can do to you....2 frame hit with dair or aura sphere. d-tilt or d-smasht he ledge during the 2 frames. Reflectors hurt lucario's off-stage game a lot. Be wary of getting up from the ledge if Luca is charging an aura sphere. If u get trapped by it in shield, shield sdi into the stage, then back to the ledge to escape. If i try normal get-up or jumping off ledge, you risk getting JC up-smashed or baired. If you roll in, you get the aura sphere. All of these can kill. What's best is to drop down, up air through the stage and regrab
after Lucario has a full charged aura sphere. If it's not fully charged, he can just go back to charging it again on the ledge. If it's charged, he must throw it, though he can of course throw it at you as you regrab the ledge
Key to the matchup
Don't be scared of aura. Lucario may be able to kill you at 30 with an f-smash, up smash, aura trap up smash, force palm, etc once he's at Super Saiyan % (120+), but the problem is that he must land those things. Most common to hit you are aura charge>up smash or force palm reads/mix-ups. To counter Lucario's aura, it's important to understand how Lucario is moving at earlier percents. If they are playing a no-force palm-allowed game, look out at high percents for the force palm. If you're getting caught by aura sphere charges, remember to hold shield, don't try to drop it, and shield sdi out. Shield is your friend. Spot dodging is not. Unless you're 100% confident in spot dodging, it's generally going to be fairly bad for Zelda as her options are too slow to take advantage of Lucario afterwards or you'll get hit anyway by attacks. Spot dodging normal grabs is sorta ok, but only if you can get an optimal punish off of it.
Also, Elevator is super risk. Only do it once per set, once per game if you must. Else you'll meet down-smash and die.
I'd give this matchup a 50-50 tbh. Lucario has a lot of trouble vs characters with strong defenses. We have to bait out options and we can't just overrun you then kill you with low percent on our side. I don't give Zelda advantage because, well Aura, and you can't rush down us like Fox can, and you don't absolutely shut us down like Ness, but Lucario can't take too much advantage over Zelda either. It's a very frustrating match-up on both ends.
Anyway, this is how I feel on the matchup and how I've seen it played/played it in the past. Also
T&C, Lylat, Delfino=Zelda advantage
Battlefield, Dreamland, SV=Luca advantage
FD, Duck Hunt = Neutral imo
All other stages aren't played. Lucario bans Delfino and Halberd if legal. You ban BF and SV. You have low ceiling advantage, but I like BF and DL for platform movement around you.
Edit: Zylach, I didn't even read your post on the MU. Glad we both agree it's frustrating and 50-50.