I know people who spent like 10k golds in both chests and in luck glow and still hasn't gotten dzerug & cerrador ones, and i know people who spent like 200g on luck glow and about 150 or so in chests and got both. So yeah, luck is a weird thing lol.
I myself haven't got jacksh when it comes to these two. Others I got fairly easily, spent over 1k gold on luck glow and didn't see dzerug, for cerrador, didn't spend much on chests tbh, maybe 500-600g so I can't say anything.