Representing oneself is very challenging. One of the forms of the challenge is that in order to be able to argue in court, one needs to have an extensive legal knowledge, also of past cases. Gaining this knowledge takes years and so for example there might be some legal precedent that could help Zac, but he won't know it.
Another thing is that with little experience, he won't know what kinds of things are effective in court and which are not and as such, he might not be able to convince the Jury as well as his lawyer.
