@Austin Bright,
I'm not a wholesaler. However, I've done these things to find zip codes:
Contact property managers in the city and ask for advice. A great PM will know everything about a city, as well as a great deal of information about the zip codes they do business in. They will be willing to share.
Go to the city's economic development website, read their "Master plan" or "Economic Development Plan" aka "Comprehensive Plan". These plans will highlight opportunity zones (OZ) that identify the path of progress. You want to make sure you are ahead of the path because all the investors and wholesalers that were there before you will be looking at OZ for the Tax Benefits.
Look for recently passed or proposed bills that affect Real Estate(Local, State, Federal).
If you can drive for dollars, do so. It'll give you a real good idea of what the neighborhood "feels" like. As well as find potential vacant properties which you can wholesale.
As @Tim Lee said, find cash sales. It'll likely lead to investors and where they are buying. As a wholesaler is to learn their process and make their job as easy as possible.
I research market trends, learn about the market cycles (Recovery, Expansion, Hyper Supply, Recession). Master that, you'll never run out of zip codes.
Set daily alerts on websites such as Zillow to make sure I know every home that comes on the market and how long they are there.
Attend meetups, network, the great thing about this time period is that most are virtual.