The 26-year-old agreed to join the Blues in a £37.8million deal in February after signing a five-year contract, with his transfer from Ajax originally scheduled to go through at the end of the domestic campaign.
But Fifa's decision on Tuesday, April 7 to approve plans to relax the regulations on contracts and transfer deals, as a consequence of the coronavirus pandemic, means some deals may be altered.
World football's governing body has published guidelines to help clubs and leagues avoid the myriad legal problems posed by the Covid-19 shutdown.
Leagues across the world have been put on hold in the midst of the pandemic, with the Premier League and Football League having been suspended indefinitely, prompting a number of issues as to when the season could end.
Notably, Fifa's guidance on outstanding transfers and loan deals suggests Ziyech will stay with the Eredivisie champions until the Dutch league season has been concluded.
The statement reads: "With the current suspension of play in most countries, it is now obvious that the current season will not end when people thought it would.
"Therefore, it is proposed that contracts be extended until such time that the season does actually end."
While this will come as a disappointment to Frank Lampard and players such as Mason Mount - who publicly stated his excitement in linking up with the Moroccan - the inconvenience for the west London side is minimal at worst.
Under the original terms of the deal, Ziyech was only allowed to be registered from July 1 due to transfer regulations.
While some European seasons could be extended beyond that date, it is still conceivable that Ziyech arrives at Stamford Bridge on the agreed date if Ajax's season finishes before then.