Older versions does indeed mean more bugs and less features. But if you can't use the newest version, that can't be helped. You could always get the DOS version of the latest ZSNES. It's on ZSNES.com, along with older versions of the emulator.
Edit.
Apparenly, absolutely all versions of ZSNES for windows require DirectX 8 or later. DX8 should work on 98, as it has done so on my Win98 computers in the past, so either try fixing your DX8, or use the DOS version. Alternatively, you could throw out the abomination that is Win98 and install WinXP.