A2000 has 5 Zorro II slots
A3000 has 4 Zorro III slots
...in the case of the A3000, the Zorro slots are inline with a video slot, so if you've got a video card installed, you've got 3 Zorro slots left. I believe the A4000 is configured just like the A3000 when it comes to expansion cards, 'cept it might have one more inactive ISA slot.