Well, the Fastlane is good, but it is also rare and expensive. And it is surely overkill for what you plan :-D
Options:
a:Get an accelrator, most of them have a controller onboard, and even one with only a 40MHz 68040 will drasticly improve speed compared too the stock 25MHz (mainly due to the accels having RAM onboard).
b:Get a Zorro2 card for the A2000, those are cheap and more than fast enough for a ZIP. But stay away from C=2091 and GVP unless they have the "GURU-ROM". Also make sure that you get an RDB-compatible one, meaning get one produced in the 90's. An A.L.F3 or Oktagon would be my prefered choice.
AFAIK there is no limit on what size the A4000-IDE will take HW-wise, but you will need special SW (as included in OS3.5/9, or available on Aminet), to make use of anything beyond 4GB.
