People read the whole situation the wrong way.
Rebirth is not the game cucking Zack and making fun of him. It's the game where Zack's love for Aerith knows no limit. Marlene scene is not here to confess Aerith feelings to Cloud. It's here to show how Zack will ALWAYS prioritize Aerith.
"The woman I love may have forgotten me and is loving someone else ? Someone whom life is between my own hands ?" And what Zack is doing the very next scene ? He's going to Hojo to save Cloud. Because he's been told he'll be the one to save Aerith
All of this is just to doubling down on Zack being the PERFECT boyfriend. Because they know how the Cult Clerith talked shit about him. It's the dev telling "See ? That's why everyone loves Zack and why he'll be the perfect match for our flower girl"
People really need to look at Rebirth properly and you can see just how much it sets up Zerith
Aerith herself says i saw Zack in you to Cloud similar to OG but now we have context with how Zack acts and its not that much like Cloud honestly. So its quite sad actually, that Aerith is wishing for Zack so bad she is seeing Cloud as him.
Aerith speaks to Zack's parents, with Tifa then asking if there where any letters. So we know offscreen they have had a conversation about Zack and Aerith has told Tifa about her love for him.
Aerith tells Zack's parents that Zack probably had lots of girls. This isn't actually something Aerith believes; she's in denial about Zack's death and instead of acknowledging it she's coping. Aerith, in crisis core felt Zack's death instead, she's not accepting it.
Aerith also saved Zack since the whispers in the remake showed her specifically the final stand of Zack and she's changed it this might be what Sephiroth wanted.
Aerith and Zack both have the same dialogue, almost word for word, about "the future isn't set in stone"
The Marlene dialogue is about like, then Aerith says there are different types of liking.
Zack ties her ribbon around his hand.
Zack's storyline is all about trying to reunite with Aerith and wake her up
Everytime in this game Zack ends up at the church no matter what including the ending.
The yellow flower petals are always flying by Zack and leading him places.
Cloud mentions that Zack is head over heels for Aerith. Why add this in as dialogue
We get multiple scenes of Zack speaking about Aerith, even describing her to Cloud.
Zack and Aerith touch hands across the lifestream (soulmate stuff)
Aerith admits she still has feelings for Zack
The game shows Zack stroking Aeriths cheek at the start of the game.
Zack even when learning about Aeriths feelings still shows how dedicated he is to Aerith. Though hes probably wondering how comatose Cloud even knows her but is more focused on trying to save her.
In this game it seems couple characters mirror dilagoue (Tifa and Cloud) (Zack and Aerith with hellooo in there)
The date scene cuts between Zack and Cloud doesn't know where Aerith's favourite place is yet show Zack already at the church
They mirror NPTK with Zack also catching the petal and holding it but he lets it go and it leads him forward.
They have made new players root for Zack and built up their reunion to mean so much more than if it was in this game, Now not just crisis core fans but new fans want to see Zack get a reunion, He doesn't really get a win this game so for the next game any win he gets will mean so much more.
Cloud calls Aerith weird we can directly compare this to Zack saying normal is overated Cloud didn't mean to say this but we know what she thinks about being called weird.
Every crisis core reference showing that does exist is canon and will have to resolve the letters and the reunion