I tried building a zstd dictionary for something(compressing many instances of the same Mono(.net) binary serialized class, mostly identical), and in this case it provided no real advantage. Honestly, I didn't dig into it too much, but will give --long a try shortly.

PS: what the author implicitly suggests cannot be replaced with zstd tweaks. It'll be interesting to look at the file in imhex- especially if I can find an existing Pattern File.