These factors collectively contribute to a successful sale and maximize the property's value.

1) I always use zillow to list new properties and use there platform to accept zillow applications2) Doorloop for management that includes accounting, repository for documents like leases, collect rents, tenant communications3) Received lease agreement from a lawyer

I am considering other options to see if there are ways I can hire someone to just do showing only and mamage my own rent collection through Zillow app, I also have my own contactors to do maintenance but have been paying monthly fee to my property manager who has done literally nothing, they also never answered my calls.It definitely sounds like you need to reevaluate your relationship with your property manager.

Your tenant stayed somewhere with bed bugs and brought them back in their clothes/luggage, or they bought used furniture that already had bed bugs.

Payment methods, tax collection etc.

And you avoid things like damaged properties (guest insurance from airbnb or prop manager themselves cover that), evictions, collections, etc.   

He collected first/last/security payments prior to move in date and was never heard from again.

Airbnb for sure collect data by letting you use the sync calender.

They have to collect the data, confirm the data, then publish the data for the public.

Did you collect and keep an earnest money deposit from that buyer?