How much does access cost? You're making a massive purchase. If that data is going to help you save a substantial amount by finding a diamond (or even some lesser precious gem) in the rough, it seems like it would be worth a few $hundred to save much more than that.
There are distinct differences in these approaches. Zillow’s data lags 3-4 weeks while HouseCanary’s is about as real time as you can get. MLS can be weird and is typically market-specific. With all of that said, you can’t just login to a website and have this available. There is legwork required.
It looks like Zillow offers an API [0] though I'm not sure of the extent of its capabilities. Could be you don't need to go the scrape/captcha route though?