I was able to play Moto Racer 2 in DirectX 3D mode on Win 7 after i copied the 12.8 version of atiumdag into the game folder . That solved the z-buffer error problem . But the same solution isn't working anymore on Win 10 x64 .

Do you think the game will run with the 13.4 Beta Catalyst display driver on an HD 5850 ? Does Win 10 supports this old driver ?

According to the wiki won't launch properly on Windows 10 without dgvodoo.

Already using dgvodoo with the game but the z-buffer error remained .

Hmm, maybe try the latest drivers for the HD series?

http://support.amd.com/en-us/download/desktop/legacy?product=legacy3&os=Windows%2010%20-%2064

Already installed .

I am afraid that at this moment you're out of luck.
I couldn't find anything else to help, sorry. :-/

No problem . Thanks for your help .

Bump .

And fixed .

https://www.gog.com/forum/moto_racer_series/solution_for_moto_racer_2_not_enough_video_memory_for_the_zbuffer_error