Zenith De Luca's are great watches and still massively undervalued IMHO. That being said though it all depends on conditions, if they have Box and Papers or not and which series they are.
The first posted in the OP is a first series, which is BY FAR the most desirable and soft after, especially with the black dial (that even though slightly less rare than the white dialled first series - ~ 1050 pieces in black vs ~ 800 in white - it is more wated and IMHO looks better and more vintage) must carry a (big) premium over later series, that look more modern and less vintage, are collectively less rare and IMHO look more like a Rolex wanna be.
Being the watch not that old (not even 30y for the 1st series, that dates 1988/89), the key is condition and if it has box and papers, which the younger the watch the more it is expected: to me a top notch first series in great conditions and correct signed papers and box should sell in the 4/4.5k USD range, depending is it has been serviced or not. If without box and papers I would take out 500/750 ISD form this, but I expect this gap to grow as time goes by and box and papers exaples will find permanend homes in collections. 1st series De Lucas are climbing relatively fast, but they are still unappreciated IMHO.
The second posted is a second or third series with white dial: again I think conditions and box and papers are key. That being said a second series De Luca should be ~ 2.5/3k USD, even though I see them for more but they don't really sell.
If you go quickly in C24 you will see that there re a lot of De Lucas, but very few 1st series and in face no 1st series with black dial.
Very nice watch indeed!