Does Paid Premium Avast Protect against Zero Day Exploits?
First, I’m an Avast user and not an Avast Team member.
By its nature Zero Day exploits have no notice. So other means have to be employed to protect against this.
Behavioural Analysis, Heuristics, Sandboxing (new, unknown files), Anti-Exploit Shields etc. The idea being to prevent whatever this zero-day exploit might be from getting on your system in the first place.
It rather depends on the location, which presumable have been external to your system, the above would be a potential defence against this. There is no 100% protection out there and Avasts Developers would be on the look out for this.
As for does the Paid Premium version specifically protect against it, I would say not specifically only the paid versions. The developers I have been using Avast Antivirus Free for over 21 years without bumping into this issue.
Given its nature, Zero Day Exploits, can anyone give 100% protection guarantee ?
It also depends on the user sat at the keyboard, do they visit unknown sites, some people have a greater risk of hitting malware in general by their habits.
Interestingly someone has posted an image, not directly related to zero day but gives an indication of some of what it is looking out for.
There are other Shields which may be involved.
Compliments to [Ioannis9] who posted this image, though not specifically related to your question.