A lonely stoner scientist develops a method for reversing zombification thanks to a girl he used to smoke weed with then sets out to find and cure his girlfriend but ends up having feelings for his old friend on the way.

The current version is confusing and completely buries what seems to be a potentially interesting?story hook: the discovery that pot can immunize the general population from becoming zombies.? Unbury and focus on the story hook.

The current version is confusing and completely buries what seems to be a potentially interesting?story hook: the discovery that pot can immunize the general population from becoming zombies.? Unbury and focus on the story hook.

So everybody in the movie is stoned? And when they don't smoke enough they turn into zombies? I don't see how it's only this scientist who is able to figure out the obvious connection.

This buddy romance, how does this relate to the main plot? If it results in being the main romance, doesn't it undermine the protagonist's goal to get his ex back? What's the adventure they go on and how does that relate to the main plot?

If his ex is controlling and superior why do we want him to get back with her?

Are the teenagers the antagonists?

Your characteristics for the protagonist are that he's lonely and a stoner... this suggests his arc is to find somebody and not be a stoner. If you want to suggest he lacks confidence and uses the weed as a coping mechanism then suggest that instead.

Honestly, I would simplify the story. The best stories are remarkably simple when you break them down. All the elements fit together.

When his ex-girlfriend is bitten by a zombie, a timid bio-chemist with a weed habit must develop a cure if he's ever going to win her back.

This version, while not perfect, has a strong inciting incident, his characteristics suggest an internal arc, an occupation that matches the demand in the story, and the weed element (which hints at the stoner side), a clear goal (although arguably two goals that are interconnected) and does away with everything that, in my opinion, isn't necessary. You can still have the subplots and teenagers etc but I think they are superfluous in the logline. They don't change the primary goal. Again, this logline isn't great - it's not particularly exciting and doesn't do much to suggest the world they're in, but you get the idea.