William Henry entered the Dutch cavalry in 1672, but was better known at The Hague for his good looks and gallantry, and as a companion of the prince of Orange.
He was trusted by the prince, and acquitted himself well on a mission of observation to England in August 1687, the nominal purpose being to condole with the queen-consort upon the death of her mother Laura, Dowager Duchess of Modena.
His avowed purpose was now to felicitate the Queen Consort, Mary of Modena, on the birth of a prince; his real object to inform himself about the nation and to gauge the probability of James II's summoning a parliament and adopting a more conciliatory policy.
He returned with Sidney to The Hague early in August, taking with him letters to William from Nottingham, Churchill, Herbert, Bishop Henry Compton, Sunderland, and others.
On 15 December he was sent by William from Windsor with a message urging James to stay at Rochester and not on any account return to London.
In response to William's blunt message, James expressed a hope that the prince might be induced to meet him at Whitehall.
Zuylestein was ready with an uncompromising answer to the effect that the prince would not enter London while any royal troops remained in it.
In July 1693, in the sanguinary battle of Neerwinden, after distinguishing himself, Zuylestein was slightly wounded and taken to Namur; he was exchanged and returned to the camp on 8 August.
On 25 January 1681, William Hendrick married Jane, daughter of Sir Henry Wroth of Durrants, Enfield, and of Loughton House in Essex.
Ken prevailed on the count, and himself performed the wedding ceremony secretly in Mary's chapel while the prince was absent hunting.