I just heard about this case after listening to a True Crime Daily podcast. Shocking and bizarre stuff.
This is purely anecdotal, but I wanted to add my observations and thoughts about ZH considering what I know from my experience as a classical pianist who also graduated from a famous conservatory in NY and performed abroad.
First off, I know some think of musicians as more "sensitive" (they even said this on CrimeWatch) and for some, that is definitely the case. But not all are like that. Some musicians are great technicians which lends them success, but they may be quite robotic and not at all expressive/emotional in their performance or their personality. These people have pursued music performance mostly because they love the attention and spotlight.
Re: the Marine Corps Officer Candidates School, it seems to be a 10-week program which includes physical training among other coursework. According to Wikipedia, "the Officer Candidates Course, which is designed for college seniors or graduates and enlisted Marines, and consists of one ten-week training session. While the curriculum is identical to the 10-week PLC Combined session, OCC is held three times a year (winter, summer, and fall), and accepts only college graduates." I can say that it is quite unusual for someone serious about a career in piano performance -- especially at age 27 when you've more recently graduated and you want to take advantage of your connections from attending a prominent school, etc -- to take 10 weeks off away from any piano practice facility. I know I wouldn't travel anywhere unless I first researched where I could practice while gone. I also know that around his age (late 20s) was when I began yearning for a regular income and that is when I switched careers, eventually earning a PharmD. I tried doing both pharmacy and piano, but it's just not the same. You have to dedicate yourself 100% if you want to truly "make it" at the highest level in classical piano performance. So it seems to me he was definitely trying to leave the profession at that time but injury pulled him back to music.
From his achievements and scant awards listed, it sounds like he was decently successful as a teenager (one small int'l competition win at 18) but since then hasn't really achieved anything particularly remarkable. He seems like a self-starter who networks and has gotten himself a couple cool gigs, but I can also see why he was thinking about joining the Marines: he was probably running out of money. All the music gigs described in his bio make VERY little money. Probably some he is doing for free! So he may have been very strapped for cash.
Another thing I'll mention is that in music school in NY, I was shocked by how common drug use was. Hard drugs. I never was around it because I had no desire to do so, but even my famous piano professor asked us once in our studio class if anyone had suggestions on how to smuggle some drugs in from France. She also even told me I needed to try certain drugs to enhance my performances. I still remember her saying "To understand and play Scriabin well, you need to do mushrooms" (I didn't). So my next concern would be that perhaps ZH was using drugs or needed money for drugs and maybe that played a role in the murder. Unlikely, but possible.
I really can't see ZH going out of his way to murder someone as some sort of vigilante. He comes across as very self-absorbed and concerned with how he is seen by others. He wants to be in the spotlight but not a bad spotlight. Maybe he did have a sicko side to him, though, and that paired with his [speculated] financial woes pushed him to accept a murder for hire position. If he were hired to kill CLP, however, why would the most likely person to hire him still be free and posting on social media?
Anyway, I hope sharing these insights & observations might spur some ideas from other posters here. It's surprising how short this thread is considering how strange and compelling the case is. I would love to hear others' thoughts!