As such, the much discussed Base Delta Zero makes was logically bound to return. It's an iconic concept well known to hardcore SW fans.
Wookiepedia is constantly updating its database and I must give them my kuddos for going through the entire tedious work.
Their BDZ page will list all new references from the Disney-era canon.
From the Star Wars Rebels: Sabine My Rebel Sketchbook; Sabine Wren, in her private journal
I believe more references of that type will creep in with time."That 'Base Delta Zero' initiative the Empire keeps talking about? The new 'key to planetary liberation?' Don't believe it. It's a military code phrase, and it means TOTAL EXTERMINATION OF A TARGET POPULATION. It's completely loathsome."
There also are mentions of it twice in Rebels.
First in the episode Rise of the Old Masters and then Empire Day.
Transcripts.
The first does indeed have a ref to BDZ but it's presented as a positive action according to imperial propaganda.
A quick search for key words in the next episode didn't return anything though.
It's also mentionned in a book but there doesn't seem to be any valuable information to extract from it.