Sports mode improves pickup, however I would still struggle while sudden braking at higher speeds . 2nd gear is very sluggish. e.g. IF I am running at 50 Kmph in 3rd gear and changes to 4th gear, RPM suddenly drops to 1200-1000 range and then even if i push full throttle , car does accelerate .Finally i have to shift down , throttle it again , take the RPM to higher REVs and then shift. what i have noticed if RPM dropped below 1500 RPM car does not picks up but if i keep pushing it hard in higher rev range then it picks up and practically its highly impossible to keep RPM that high.
I read similar issues from other Zest owners in Zest FB page as well. Might be a problem with few Zests as you are not facing this issue. you are lucky in this case.