Most automatic transmissions act just like you're saying if they are starved for fluid. The fluid in your transmission does three jobs:
1. Lubricant - It's the oil for your transmission just like 10W30 is for your engine.
2. Coolant - It's the coolant for your transmission just like the Prestone is for your engine.
3. Hydraulic fluid - This is where it gets interesting. All the "gears" in your transmission are selected hydraulically. The valve body in there moves little pistons and actuators to engage and disengage various gears and clutches to conform to the gear it's supposed to be in at any given time. If there's not enough fluid, the hydraulic pump sucks in air and renders the entire hydraulic system inoperative. If there's plenty of fluid but there's a restriction on the intake of the hydraulic pump, it won't develop enough pressure to actuate those pistons and other components to their full potential and you'll get slippage.
The primary and most common reason for your symptoms is a clogged filter due to lack of maintenance. Most people still to this day think that automatic transmissions can go 100,000 miles without ever looking at them. Ain't gonna happen. Most manufacturers recommend 50K - 75K. I go with 30K or less. Complete fluid and filter change. And if you're driving a Mopar product? Shorten that interval down to 15K or less.
The next most common reason for your symptoms is lack of fluid. Meaning it doesn't have enough in there.
Last but not least is component failure, generally brought on by one of the above two symptoms.
First and foremost, drag it to a shop so someone can do a fluid and filter change on it. Don't bother with a flush. Not at this point. Not worth the extra cash if the transmission has been neglected to the point of component failure, you'll be polishing a turd. Do a filter and fluid change (yourself if you have a Hayne's manual, it's really not that hard) and get back to us.
If the symptoms go away, you dodged a very expensive bullet and all is good. If the symptoms improve but are still there, you're looking at some very expensive transmission work in your very near future. If the symptoms don't go away, you've got a decision to make as to whether the Zuk is worth the expense of replacing the transmission or not.
Oh, and check the shifter cable and the TV cable as well. If the TV cable is toast, DO NOT drive it. It's the quickest way to burn your tranny up if you do.