Zorin link missing

[Bourne]

I checked if I can download old Zorin 15.3 but the link is missing.
Then if I would buying new version Zorin 18 then the product what I bought will be no exist example Zorin 17?

[zabadabadoo]

You can find it still at the download mirrors. e.g. Index of /zorinos-isos/15/

[Bourne]

Version Ultimate what I bought?