Not sure who the right comparison is, certainly not Oliver Miller as Zion lead the Pelicans to one of the best records in the conference for a big portion of a season. Yeah he can't stay healthy though and also has some off the court stuff that is perplexing at the least.
Maybe Shawn Kemp is a good comparison for him. If he had the right teammates and things go right he could help get a team to the finals.
Or he could sit on his ass, get out of shape, and be a horrible backup earning $100 million+