Zeke had a nice relationship with all the girls in the CHGH. He’s the only boy by default when they all hang out together, but everyone sees him as their brother - because they can all say “we knew each other [or at least Lilo] as kids”, there’s just not a weird vibe between them all for having one guy and five gals. They have one thing in common: Lilo! She’s the glue keeping the group close.
Mertle - Z’s relationship with Mertle is by far the funniest to explore. Mertle acknowledges that Zeke is “the big band hottie on campus” but she's not interested in dating him, and whenever he’s got a gig or some advancement in his career as a musician, Mertle downplays it (because she still likes to feel like she’s the center of attention). She calls him “Freak Lau” because he’s got a lot of the same interests as Lilo, and when they met, Mertle assured him he was cool enough to hang out with them and decided anyone who had so much in common with "Weirdlo" had to be given his own nickname. They tease each other a lot, and Mertle's threatened Zeke's life if he ever hurts Lilo, but all in all they get along.
Victoria - Victoria and Zeke are thick as thieves. They have the exact same sense of humor, and they both think Lilo is the best, and they're both pretty good musicians. Victoria will often sit in on Zeke's band rehearsals and sometimes fill in on the drums for fun! (Lilo doesn't love that but quickly matures past any petty jealousy, because come on, it's Victoria.) They're especially good at pulling pranks together, and making fun of movies. Early in the Zelo dating relationship, Lilo is feeling like Victoria might be a better match for Zeke, but she soon learns that that's a ridiculous way to be thinking.
Teresa - Teresa and Zeke don't interact as much as the others, because Teresa always seems focused on something superficial and Zeke's not like that at all. They're friends by extension - Teresa is best friends with Mertle and the others, and the others are best friends with Zeke, so Teresa is also, by default, best friends with Zeke. Teresa is the one who loves to give advice on dating to Zeke, and criticizes his outfits, and goes to gossip with him all the time. Zeke's a very good listener, because he's the quiet type, so when Teresa has a juicy bit of info on someone she just "has" to get out, she grabs Zeke. Zeke understands Teresa is probably the most insecure out of the girls, especially about her appearance, so he often makes sure to compliment how she looks if she ever asks.
Elena - Elena is a giggler, and an animal-lover, and a terrific chef. She wants to open her own diner on the mainland, and Zeke discovers that he really likes everything she makes. (His favorite is her clam chowder.) They're not super close, the same way he's not super close with Teresa, but they get along just fine! He's always very sweet to her because she's that friend in the group who starts telling a story, and everyone stops listening (not on purpose) after a few minutes, so she just feels embarrassed and ignored, and Zeke is usually the one to quietly be like "keep going, I'm listening". He's really good with women guys-
Yuki - Yuki doesn't go to Honolulu University, but she does visit from time to time, and she met Zeke a little later than the rest. He's not the sportiest guy, so he can't really appreciate her hockey affinity, but he does like her zany sense of humor, and the way she blurts things out without thinking. He once told Lilo that when Yuki's in town, you tend to learn something new every time. But they don't see her much.