- Be careful with Din's Fire, it can be punished easily. Use it when the enemy is far away, preferably when he is off stage.
- A good way to edgeguard is to summon these phantom soldiers with down B. This works against opponents approaching the stage in a rather horizontal angle or from a bit higher. Fully charged the phantom soldier has much knockback and quite a range with the sword which might surprise the enemys a few times. Zelda isn't very common (inb4 Sheik) and not even all Zeldas make use of down b.
- Zelda has competents throws for killing, but I guess she has a rather long ending animation on missing grabs. I'm not sure about this though. Down grab can lead into a quick nair which is more reliable than uair.
- Practice using up B (Farore something I believe). I guess you figured out how to recover with it reliably. I mention this because I had some trouble with recovering into the right direction when off stage. But it is also an useful technique for attacking. One option is to teleport horizontally on the stage to attack an enemy on stage. In FG it might work once or maybe twice on deliberate spammers, but experienced players will easily shield it. It can be used as a punishing tool against characters like Link or DHD though, but you need good reflexed to avoid their shield. Another important aspect is the use of UpB as a finisher. Use it against opponents in the air and it will kill fairly early. It's kinda risky, but works fine, especially against the try-hards you seem to struggle with. You can also try to approach the opponent, to use UpB with a vertical, upward direction and to hit them twice, eventually taking a stock from them. I've seen better Zelda players doing this with me, but I don't know how to pull it of.