Comparing expression of a gene from different datasets in cBioportal

Question

[Lordegod]

Hello, I am very new to RNA-seq data and have no bioinformatics background. I have downloaded two datasets from cBioportal (TCGA, and a dataset from a published paper) with the goal of comparing expression of a gene in different prostate cancer subtypes (TCGA - adenocarcinoma, Published paper - other subtypes). Is the "mRNA_expression_median" or the "mRNA_expression_median_Zscores" file from the two datasets comparable? How will I go about this and what statistical comparisons can I employ? Thank you so much!