Bangalore to Mysore

Yup. You should be able to. It depends on which day though as there could be traffic at the entry and exit points of the expressway. Leaving a bit earlier would be better.

Better to stay for a night.

Zoo will take 3-4h easily as it's big compared to others.

2h each for palace and church.

Do visit chamundeshwari temple, without that Mysore visit isn't worthy. Mysore got its name from this temple.

If u r a hustle person then complete within 16h else stay a night 🌉

If traffic ⛔ woes then u will be stuck

Better to leave a little earlier (say 4-5 am). That way you can directly reach chamundi hills by 7am, have breakfast by 8-8:30am and by that time some of the tourist spots will be open.

If you leave Kengeri around 8 am, it's possible to complete your day as per the above plan.

If you are thinking of starting from place in Blore which is atleast 5-10 km away from Kengeri, then one day trip will be exhausting. You may need atleast 2 hrs to cross Kengeri and enter Expressway

Stay overnight if you start at 8am