The Dutch fish you are talking about are obviously in brackishto salty water (which zander can survive & even thrive in)due to the presence of herring, because they certainly don't live in fresh water,therefore they must have been a constant food source for many many years, so there is no comparison to Fenland zander, unless you know a drain where herrings are & have been present for a thousand years !
I can't comment on your catching zander on sea baits, all I can say is that in the last 25+ years of fishing the drains for pike & zander I have never caught a single zander on sea baits, so for myself I would be mad to use them when I have perfectly good lives & fresh deads in plenty.The only "sea bait" I would even contemplate using for zander is the smelt as they do run up the Fenland rivers, but even saying this I don't use them & probably never will. As I said earlier, I can see no point in making it harder than it already is.
As for logic re sea baits being less appealing to zander, I have none & don't really care. I just know they are not productive for me so I don't use them & thats all I care about.Herrings and zander are not& have never been a constant & indiginous food source for zander, where fresh fish, eels etc have sothis is what I use. If they are used to, & quitehappy eating fresh fish why use something they don't see swimmim g around & aren't used to eating. Zander are not tackle or bait shy & eat live & dead frsh fish every day so why change ??
If it works for you then great, carry on using them but it's certainly not for me &I wouldn't advise other novicestouse them,butcertainly wouldn't ever saythey won't catch on them. As I wrote in my book, with zander there are no rules.
Further to this, if it's not broken why fix it ??