International students can study two or more courses on one visa which is called course packaging. While doing the course packaging there should be a reasonable course progression from one course to another. For example, you can package a Diploma in IT course with a Bachelor of IT course. Applicants with limited or no course progression will be considered against Genuine Temporary Entrant (GTE) provision.
In course packaging, the highest-level course is the principal course and is used to determine the applicant evidentiary requirements
If you provide CoE for all the package courses, then the visa may be granted for the full duration of the course- not exceeding five years.