Depending on how pricey the transaction - there may be limits to how much you can transfer through Zelle, Venmo, etc.. You'd have to take a look at those to see. I should mention that I was surprised to receive a 1099 from PayPal where they reported my PayPal income to the IRS because they are now obligated to when you receive over $600 in any year.
Cash is always King - money order or certified check works well, too!