Spools are only 20 bucks or so and there's already threaded holes welded on the swingarm for them. To me, they're well worth it considering how much more stable a spool stand is.
With that said, if REALLY don't wanna spend the money on spools, you can purchase a pad stand which grabs the bike by the swingarm itself w/ little rubber "hands".
With THAT said, i have a pad stand for my ex500 and i hate the friggin thing... My EX always slides around on the pads, it sucks so i may get some spools welded directly onto the swingarm.
I 110% suggest getting spools & a spool stand and for that, I have to recommend
Woodcraft. Best quality out there, bar none, tried & tested.
As for the center stand on an older gen ZX or ZZR, no, I've never heard of it being done and I imagine it wouldn't be easy w/ the fairings the way they are. There's simply not enough room. Not to mention you need solid mounting provisions underneath the swingarm pivot area which the bike does NOT have.