Is it possible for me to use my home-built CNC router on Wenge or Zebrawood boards? The board feels heavy and the shop teacher told me that it's very hard wood. Another shop teacher bought a piece but I'm afraid to use my home-built CNC router on the board because the bit may break. Any suggestions such as slow feed rate and/or low spindle speed? The fastest feed rate is 20 IPM and the fastest spindle speed is 30,000 RPM but I use a speed controller to slow it down to 20,000 RPM.

that wood is tough but not that bad.cut a sample piece and mount it in your machine and do some easy passes so you can see what your router can take.30,000 is not bad.
set your feed rate and cute depth slow and shallow then work your way to a heavier cut.and pay attention to how your cutter reacts .go get em!
bill

Slowing down will create more heat which would make it more likely to break a bit. Cut as fast as your machine will allow, but just take shallower cuts.