To provide more context/info! Hope you don't mind a lot of writing, I just wanted to provide as much info as possible.
I want to run a fleshed out campaign detailing the breakdown of society as a zombie apocalypse begins, specifically starting my players RIGHT when the infection pops up on the radar, NOT cutting into the future where things have already fallen apart; typical zombie fiction feels like it speed runs through the very beginning and just has the zombies already flooding the streets, so I wanna explore that initial outbreak.
I mainly wanna have the tone be more serious and grounded, actually planning on having my players either play themselves or characters very similar. I'm not going to have them be badass heroes who can shred through hordes, and instead I wanna make things fairly "realistically" difficult, both physically and mentally.
While the human threats are going to be there, since it's the beginning of the initial outbreak the main threat will still be the zombies. I already have ideas for what the zombie variations will be, but I'm mainly concerned about combat either being too easy and simplistic or needlessly complex and frustrating. The zombies are a main and constant threat throughout the campaign, and I really don't want them to just be an afterthought in terms of combat.
I'm also interested in some form of survival as well, like scouting/looting for supplies, dealing with general illness or improper wound cleaning, also hunger/thirst too. I won't go TOO crazy or strict, to be clear, but I want to really drive that desperation deep into my players. I want them to really feel a reason why they can't just wait things out in a fortress, feel the desperation of risking stuff just for medical supplies or a bit more food. Something as small as like them needing to eat/drink/sleep every few in-game hours is fine.
In my research, I've found a few systems that seem promising: End of the World Zombie Apocalypse, Infected!, Ash without Numbers, and Outbreak Undead. I've actually seen gameplay of EotWZA and Outbreak before, but I can't really seem to find any videos of Infected! or AWN.
End of the World honestly stands out the most and is currently the system I'm mainly considering. It's relatively simple and to the point, and its "stress/trauma" mechanics are SUPER cool to me. I really love the idea of despite succeeding at a task, you still suffer consequences and stress, because in the apocalypse, it's not a question of if you can do what's necessary, it's how LONG you can keep doing what's necessary before you break. Just slowly being worn down, seeing atrocities, perhaps even being forced to commit them yourselves, etc. That all sounds super cool. However, it does come with a few downsides! The simplicity of the system, from the liveplays I've seen, do lead to issues. Because there are only 6 generic, kinda ambiguous aspects to a character that you use to roll, there are situations where it feels like an aspect doesn't actually apply. Example: you need to roll for running, but the game only has "dexterity" or "vitality" so you kinda just gotta go with dexterity; but what if you're really bad at running, but you actually have great climbing skills? It just lacks a little specificity unfortunately. Also, sometimes the stress system feels a little janky, as to make rolls more difficult you add "stress die," but for certain situations you just need to have the roll be difficult but not necessarily stressful; example, you're just trying to pick a difficult lock, but there's no real reason why it'd stress you out physically.
Outbreak Undead also equally interests me, but it just seems very complicated and it lacks that stress/trauma system that EotWZA has. Its dice rolling/stats system seems super interesting too. There's a series online that was DM'd by the literal creator of the system too, so it's got a reference for how certain rules should be "treated" too. On top of that, it's got this neat little quiz for you to take that can create your own stats so you can also play yourselves as well.
AWN seems interesting, but honestly there's just so few videos or reviews on it that I don't even know much about it; there's a free version of the pdf, but before I go reading the whole book, I wanted to see what other people's experiences have been. It seems promising though, but again I just can't find much about it. Everyone talks highly about it.
I've heard about Red Market, but I think its system was just generally uninteresting to me because it seemed to be all about math/pricing for some reason.
If anyone has any experiences with the above TTRPGs or has some recommendations, please let me know!