I would eliminate the names that don't really go with your last name first.
Harrison Zeilsen is a bit repetitive (
Winston has the same problem) and the S at the end of
Thomas merges with the Z in Zeilsen so it sound more like one word (
Felix has the same problem).
Personally I would eliminate all the names that end in -on/an/en because I try to avoid rhyming but it isn't a problem for everyone. If it doesn't bother you then definitely keep them on your list.
Abram - I love the name Abram. It is one of the few strong biblical names that is fairly underused in the western hemisphere. Bram is also a great nn option.
Archer - Archer is another great, underused name. It is a occupational name which are very in right now so he would fit in fine with all the Cooper's, Carter's, Parker's and Hunter's. But Archer also has the optional nn Archie which I think is super cute. Archer bridges the gap with its Modern feel/style and Retro sound.
Asher - Asher is very similar to Archer but its a bit more popular. Personally I prefer the sound of Archer, the Ash sound is much to similar to A$$ for my liking.
Beckett - Beckett is a nice modern choice and is rising in popularity. Personally I prefer the name Bennett. Beckett is a bit to feminine sounding with its similar sound to Rebecca and Becky.
DeclanDexter - LOVE! Dexter, like Archer, is another underused option that bridges the gap. It has a great modern feel/style with its stylish X and -er ending (like Xander or Xavier) but it also has a Retro sound.
Elliott - Another great name! Elliott is another one that is rising in popularity thanks to the Ella/Elle names for girls. I think the nn Lio is super cute.
Everett - I like this name as well. It is very similar to Elliott but has the more masculine V sound that is both modern and classic/retro.
Ezekiel - ZEKE! I do really like this name, another great underused biblical option like Abram. However, I'm not sure about the alliteration with your last name Zeilsen. Sometimes alliteration can make a name memorable (like Clark Kent) but in this case both names are a bit complicated to say and I feel it creates a combination that would cause a lot of tongue ties...Ezekiel Zeilsen, Zeke Zeilsen...try saying that 5X fast!
FelixFinnian nn. FinnGideonHarrison nn. HarryLevi - I think Levi is a great name, it combines my favorite part of Elliott (LEE) and the great V sound from Everett. Levi also goes great with Zeilsen.
Micah - I like Micah, but it isn't my favorite from your list.
Noah - Noah is a nice strong, biblical option. But it is a bit overused in my opinion.
Oliver - LOVE! Like Levi this name combines the LEE with the V and adds the stylish -ER ending on top of that. Ollie is also an adorable nn option.
Percy - LOVE! However, the -CEE ending clashes with the ZEE in Zeilsen making the combination blend into one word.
Philip - Eh. I'm not a huge fan of Philip.
Rhett - Rhett is a great underused, simple yet strong boys name. It also makes a great nn for Everett.
Samuel - Classic and biblical, however Samuel is a very soft name for a boy and you have some great strong choices on this list. Samuel in comparison with some of these others is just a bit boring.
SimonTheodore - LOVE! Theodore is ANOTHER great, underused boys name. I think the nn Teddy is adorable on a little boy, however I personally prefer Theodore as a full name or middle name.
ThomasWinton nn. WinZechariah nn. Zech - Are you pron. this like Zach/Zachariah? Or is it pron. like Heck with a Z? If so I could see it being confused for Zachariah/Zach fairly often. If you want it pron. like Zach, I would spell it with the A.