* Vocus in talks with Sweden's ETQ on $2.3 bln offer (Adds shares, analyst comment): SYDNEY (Reuters) - AGL Energy said it made then quit a takeover play for Vocus as it could not agree on due diligence terms with the Australian telecoms company, which is looking at a separate $2.3 billion offer from Swedish private-equity firm EQT. AGL, which is seeking growth outside its slow-and-steady electricity retailing business, confirmed it walked away from the offer after the news was first reported by local media. Its shares were down 1.1% while Vocus stock was 0.7% lower.