I want to complete the Pokédex as soon as possible. I already have Adias, the Porygon2 and the dubious disk
There are two ways, depending on your definition of 'easiest':
If you mean 'least effort and time', then just trade with the code 0013 0013 to find someone else also wanting a Porygon Z, and a P2 with a Dubious Disk. However, you need the Switch Online to do so.
If you mean 'least money spent', grind for the Porygon special scan, where Porygon Z do spawn, but it will take longer than trading to find it.
