Reset Phone For Donation- But Screen Not Working

Try a button hard reset. Trying to figure out how many presses and which buttons without screen access might be problematic but I think it could be done.

A hammer will do the trick.
Beat it until the innards come out.
That's my safest way to make sure no one can access personal information.
I know your charity will be without one, but better safe than sorry

Did you at least have a lock screen enabled before? That will be good enough to prevent access to your data in most situations. Hacking past a lock screen has to be an intentional thing that most people are not going to waste a lot of time and resources on, law enforcement agencies spend tens of thousands of dollars doing so and even then it's still not a guarantee of success. It's not like in TV shows and movies where some kid just plug your phone into a beefed up PC and magically has access to everything.
So if you did have a lock screen in place, it's 'more or less' safe to donate as in most situations nobody will be able to or wiling to break past it even if the screen is fixed. If you're not sure a lock screen is or isn't effective, if you have it enabled on your current phone, have a technologically savvy friend try to get past it.

If that phone didn't have a lock screen in place, I agree with @Dannydet If the screen is a problem after that accident and you can't remove your Google account login or even do a Factory Reset, your data and the autologins for various apps to your online services will still be accessible to anyone who might be able to restore that phone to working condition again. A hammer might be your best option in this case. A ZTE Maven 1 Z812 is a pretty dated device anyway, the most valuable aspect to pass along might be its charging adapter and microSD card if you had one in yours (the card you might be able to re-use if its worth it, or be sure to copy anything you need off of it and then reformat it before giving it away.)

Just a thought: have you tried Google's Find My Device site? If the feature is active on your phone that should let you wipe it.

However if the charity want to do anything with it after repair they'll need to ask you to help, because it will be locked using your Google login (factory reset protection: after a reset you need to use the Google account that was on the device when the reset happened to get into the phone again). You can avoid this if you can remove the account before resetting, but that isn't an option here. But a remote reset like this will remove your data, so if you still have the phone you can try that.

OT: When I left my phone on an MBTA bus I used 'Find My Phone' to track it's journey and alert the MBTA lost and found department what bus it was on. That phone had gone through more cities and towns than I have all year. COVID-19 SUCKS!