Can I begin my trip in Schengen zone for 89 days and then move to UK for another 89 days?
Sure, why not? You can stay in the UK for 6 months. UK is not a part of the Schengen zone. I assume you read the discussion under the previous question concerning the Schengen zone. It is pretty simple. If you have a question about who is in the zone, just google Schengen Zone.
You have to be very careful about what constitutes 90 days, too. You literally have to count the days on your fingers. The day you arrive is day 1 and the day you leave is also counted.
I'd try to cut it a couple of days short--in case the customs official disagrees with your count.
Thank you for your reply.