How about something like this for Zone Modes:

case (Endless Mode): Player is beginning his race on randomly created track on slow speed which increases BUT to a certain level and what happens later is that track is getting harder by adding some more turns while keeping track possible to do without breaking (which u can't do anyway xd) and adding random objects on track like mines, bombs, track open sections, jumps and other stuff. Player can increase the speed faster if he feels like it (can't be decreased)

case (Event Mode): Speed is constant from the very beginning and tracks are not generated randomly in real time, they will be generated and saved by me (track section placement, mines, bombs, open sections) and listed as "track 1, track 2, and so on", they will be long, like, reaaaaaally long, and by choosing track the higher number the harder the track is.