Starship Troopers: Extermination is PvE wave/extraction shooter, from the company that developed Squad. Looks pretty fun but if you are not into that universe nor have enough friends you'd need to rely on other players as well.( basically max 12 players in 3 teams atm.) Warning: early access so if you are not tolerant to EA type of development/update cycle just avoid.

There is a couple other PvE wave/extraction shooter as well, so give them a try.( Just google that term, usually around $30 and could go on sale.)

Rocket League, this one I played since launch and really good game to start before your group all come online and then move on to other games.(since it supports up to 4v4, but usually people only queue 2v2 or 3v3 matches.)

Saving this post because it's right up my alley so now I have many new games to check out. Project Zomboid is still going strong for us, but here are some others that our group has enjoyed:

Heave Ho: super crude 2D graphics, but absolutely hilarious gameplay

The Ascent: beautiful cyberpunk-themed isometric shooter

Broforce: very entertaining pixel-art 2D platformer/shooter - we played this through to the end, which is rare for us

Overcooked: very entertaining 3D game, not sure what I would even call the genre - a "work" game?

Unrailed: similar to uncooked, but a different kind of "work"

SWAT 4: old 3D FPS, but still good

PULSAR is pretty amazing if you have a few friends to play with. It really feels like actually running a spaceship together. You can shout things like "Divert all power to main turrets" and actually mean that.