Kali_01:
I'm sure TH has her reasons, but it'd be nice if she told us what they were lol
My guess is that the desert beast subplot was mostly cut for time and because her parents' story is a whole novel's worth of tragedy unto itself and would be too much of a departure from the main plot. And it would require a lot of CGI.
The changes to ZX's story might have been required by the censors, or maybe the producers. Having the male lead be in love with the female lead and successfully plot to kill the second male lead (that the female lead loves and is about to marry), having the female lead commit a not-quite-murder / suicide with him, and having the second male lead convince the female lead to forgive the male lead after all that... Is a lot.
Relegating ZX's actions to a dream sequence also allows them to cut XL saving XY's life again and almost all of the Jade Mountain subplot. Maybe they felt one saving-her-from-a-death-coma episode (and one saving-her-from-a-crystal-coffin-and-whirlpool episode and one bug-connection-severing episode) would be enough. And avoiding the Jade Mountain subplot means less CGI and not having to involve as many characters. (I'll miss Sir Bi).