The ROI government has been working hard to up their capacity to transport goods directly from the EU but it is nowhere near where it needs to be to avoid severe delays. Nobody is going to say that publicly though and promote panic buying. When you are going from a position of having 85% of goods transiting the UK and have only two regular ferry services from the EU, even a years worth of ramping up port capacity and chartering extra ferries isn't going to solve the problem of bottlenecks should a no deal occur and the French choose to play silly buggers.
I think most companies string their customers along about timescales as they want the business, Zooplus will probably be no exception, though I hope I'm wrong on that. It's happening with the Royal Mail at the moment, they have promised companies unrealistic timescales for delivery which they just can't provide given the huge volume of parcels they are seeing, the said companies are understandably hopping mad as their customers are chewing their arses off and cancelling when their presents aren't arriving in time.
I wouldn't at all be surprised if in the event of a no deal situation they announce a phased implementation of customs control lasting a few months to kick the problem down the road and give a bit more time to prepare.