You are departing Zagreb airport around midday and you need to know how much time is needed to allow to get to the airport, is a taxi the best option or is there an airport shuttle bus to and from the city centre.
The bus departs every 30 minutes from the airport to the main bus station (Autobusni kolodvor Zagreb, close to the historycal centre of Zagreb) and v.v. and it takes around 30 minutes to reach the airport,i.e. Zagreb town. The ticket costs 30 kunas one way (40 kunas roundtrip). The bus picks up/drops off outside International Arrivals at the airport.
You can also call a cab (Taxi Cammeo, EkoTaxi, Taxi Zagreb…) or grab Uber.
Taxi is up to 120-ish kuna if by Radio taxi (the one preferred by locals – 01/1717 – for having a very fair attitude towards clients, experienced drivers, metered rides, and the widest network of cabs and taxi stands around town, so the most quickly available!). Cammeo has similar prices but takes ages to pick up clients (only per calls), similar with Eko Taxi, as there’s not so many of them, and not always in your vicinity. Here’s the airport shuttle schedule: http://www.plesoprijevoz.hr/en/page/timetable