Simplify the following text for a Grade 8 native English-speaking person.
Original: Three days after the capture of Fort Provintia , Koxinga 's troop surrounded Fort Zeelandia and demanded the garrison 's surrender by sending Dutch priest Anthonius Hambroek , who had been captured by Koxinga 's forces , as emissary to persuade the garrison to surrender .
Simplified: Three days after the capture of Fort Provintia , Koxinga 's men surrounded Fort Zeelandia and demanded it 's surrender . Koxinga sent a Dutch priest Anthonius Hambroek to ask for this surrender .