Green Line (operated by First in Berkshire) operates a bus from Slough to London Zoo every 30 minutes. Tickets cost $8 and the journey takes 53 min. London Buses also services this route every 5 minutes.
How to get from Slough to London Zoo
From Slough train to Paddington Underground Station, Tube to Baker Street Underground Station, then walk to London Zoo. 48 min £11. From Slough Town Centre, Wellington Street (Brunel Way) line 702 bus to High Street Kensington, line 27 bus to Primrose Hill, Chalk Farm Morrisons, then walk to London Zoo. 1 h 56 min £7. From Slough taxi to London Zoo. 34 min £99. From Slough drive to London Zoo. 34 min £4.