Thanx to the help of some great people at the Z88DK forum (hi alvin!) I was able to add some rudimentary support for the V-Tech Genius Leader / PreComputer to the Z88DK development suite. Just have a look at the platform called vgl to see some of my demo programs. It was quite a hassle for me to get used to implementing the necessary "newlib" I/O functions. Especially so, as they differ slightly for the 1000, 2000 and 4000 series.
Going forward, though, I recommend using just the simpler SDCC compiler if you want to get started on V-Tech development. You will not be able to benefit from the extensive demos of the Z88DK, but the overall installation and maintenance is much easier when just calling sdcc. The V-Tech headers and includes will be available on this project page or my github page soon.