Zen sits next to 4 phonetic neighbors — Zane, Zan, and Zenn are the closest matches by sound. Most share Zen's Japanese cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"meditation, absorption in thought"
"from the city of Venice; the Veneti people"
"God is gracious"
"warrior hound"
"courageous, brave (via Riley)"
"creative feminine variant of Kendal"
"deep valley dwellers"
"God is my judge"
"a carefree adventure"
"white, pure"
"rival, striving"
"little rock, harmony"
"elevated place, watchtower"
"silver"
"young warrior"
"heavenly, divine blossom"
"twilight, between day and night"
"of the sun, solar"
"mythical auspicious creature"
"star"
"dweller by the lake"
Similar sound: These names share phonetic patterns with Zen — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Japanese from Chinese Chan origins, giving them the same cultural heritage as Zen.
Rhythm: Zen is a 1-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.