> So you essentially say work from home should be banned, because that's also "running a commercial operation in a residential zone".
No, because working from home doesn't cause negative externalities imposed upon the neighbors - quite the other way around, the fact you're working from home reduces the impact of commuting.
> Same goes for piano lessons etc.
Unlike repairing a car in a shed with its door open, piano lessons should not cause noise emissions. If you're giving musical lessons outdoors with neighbors being forced to listen, you deserve everything that's coming for you.
> And regarding noise I wonder how are lawnmovers regulated if you have problem with car repair.
Gas-powered lawnmowers should be banned, and so should any form of leaf blowers, alone for environmental protection.
> My grandpa had his own workshop in his own house and can't imagine someone banning him from working from his own house, especially if he lives there longer and run shop longer than any neighbor who moved there.
Which is why things such as "grandfathered in" provisions exist. It's fine if you choose on your own to move to an area with someone running a car shop, you knew that there was a car shop, but it's not fine for someone else to move in and run a car shop or other negatively impacting business that ruins other peoples' property.