Achieving integration of Make or Zapier with HubSpot.

I have a free plan, and I needed a calculated property (in deals), but since it’s not available on that plan, I was advised to use Make or Zappier. I’ve tried, but I couldn’t get Make to automate all the properties, and the examples it generated only increased the value of one property. I just wanted to subtract between properties and calculate a percentage of a property, and of those calculations, only one property belonged to HubSpot. Is there anyone who can help me get this integration working? I’m a complete beginner with very little programming knowledge (almost none).