This is one match-up I feel you have to play quite aggressively, as the typical defensive Zard can't quite handle this match-up well imo. Samus doesn't have much in the way of good anti pressure options so her out of shield game is pretty awful. She has no effective out of shield aerials due to the height of her short hop, her USmash is slow and trash and her grab is the slowest in the game so the only really good out of shield options she has are drop shield jab and Up B. Her jab is fast at frame 3 but it's negative on hit at low percents (you can cc jab) and it sends you too far at high percents for her to get anything off of it, so as a result Up B is the only thing you really need to fear and it's very high commitment so if it whiffs she dies at 60 from an FSmash.
The most effective moves in Samus' arsenal imo are ZAir, UAir, Dash Attack and Charge Shot. ZAir is her primary neutral and zoning tool . It's very safe on block and leads into quite a lot for her on successful confirm but one thing you have to note is that it's typically done via short hopping back and doing it late (because as aforementioned her short hop is huge). Because of the vulnerability of her short hop you can answer with an approaching FAir and attempt to apply pressure from there. Also be weary of when she uses it off the ledge. It's difficult to punish so it's best to just respect it.
UAir is an incredibly effective combo tool that leads into four of her aerials depending on DI and positioning as well as Up B in the air. It deals solid damage and has a pretty good hitbox so it's a pretty fantastic move overall. One of the key applications Samus will often use this for is while falling to combo into Up B, pressure with jab or FTilt or try to open you up with grab. Although this is powerful you must remember that because her grab is slow, shielding for a little longer than normal and not instantly attempting to buffer an oos option is generally the best option. Extended shielding covers Up B and jab, while the speed of her grab allows you to then buffer something like a drop shield to jab or Fly to avoid the grab.
Dash Attack is very strong vs Zard because of his huge hurtbox so it doesn't blind spot as much against Zard compared to other characters. It's her best combo starter, covers a lot of space and is hard for Zard to punish because the late hitbox is surprisingly safe and the early hitbox can cross you up and Zard has no effective answer to cross-ups. If it doesn't cross you up however it's an easy shield grab, so you just have to be wary of how this move hits your shield. If it hits you try to DI away to avoid the UAir as FAir a significantly less threatening tool because it doesn't keep you in the air and doesn't combo for as long as UAir.
Charge Shot is scary only when charged as one good read could mean your stock is gone at around 90 to 100, even earlier with rage. It also does a ton of damage to shield so it's incredibly important to try to power shield it especially if you've take prior shield damage from a Missile or Bomb.
As I mentioned before this match-up needs to be played quite aggressively to abuse Samus' poor out of shield game. Charizard's fantastic run speed is pretty much the shining star of this match-up as it allows him to quickly break Samus' zone to prevent her from completely walling you out. Typically Zard struggles against projectile based characters but due to Samus' zoning options being fairly slow it's not too bad vs her. Jab of course is incredible, Flamethrower beats Missiles and Bombs but loses to Charge Shot (11%+) and ZAir, FAir is also amazing and BAir is pretty great too.
The final thing to note is offstage Samus is pretty easy to edgeguard. Due to her poor air physics and bomb jumping being no where near as effective as it used to be it's not too difficult to chase her offstage for the FAir, BAir or DAir edgeguard. Overall this is one of the more doable projectile character match-ups for Zard. Carefully applied aggression and making use of your movement speed is key.
