What do I repot my Zygopetalum Advance Australia in?

[Olive]

I got a zygo 'Advance Australia' from Orchids Limited about a month ago. She's been thriving since then, she got acclimated quickly and already has 2 new leaves out! The flower spike just started to fade so I cut it off, and as I understand it apparently now is the best time to repot a zygo. It's really difficult to find good sources for advance australias since they're so niche, and the whole 'are zygos terrestrial or epiphytic' debate is still raging as far as I'm aware. She arrived potted in sphag, and because she's doing so well I'm afraid to switch to a different medium (or even repot right now for that matter!)
What would you guys suggest? I leave a humidifier on pretty much all the time in my room and the windows open, so good ventilation. Temps in coldest part of Winter are generally 40-ish during the days and 30 at night (F). It can reach the 90s in Summer. Thanks in advance!