The world governing body said local officials could instead be appointed by the Pakistan Cricket Board.
There will be two Twenty20 and three one-day internationals from 22-31 May.
On Thursday Zimbabwe cancelled the tour after news of a terrorist attack in Karachi, then retracted the statement.
No top-level international cricket has been played in Pakistan since Sri Lanka's team bus was attacked there by gunmen in 2009.

The Cycling and Walking Investment Strategy includes the ambition of doubling the number of people using bikes by 2025.
Transport Minister Robert Goodwill said "sustained investment in cycling and walking infrastructure" was needed.
Cycling campaigners warned the strategy "won't be worth the paper it's written on" without sustained funding.
A consultation has been launched to seek views on the plans and will close on 23 May, with a final strategy published in the summer.
The Department for Transport (DfT) said it wanted walking and cycling to be the "natural choice" for shorter journeys, or as part of a longer journey, by 2040.
This would be done through providing "safe and attractive infrastructure" to encourage journeys on bike and foot, it said.
The DfT said the strategy marked a "major shift from short term funding streams for cycling and walking to a strategic long term approach".
Mr Goodwill said the plans would "benefit the whole of society by boosting the economy, improving health, cutting congestion and improving air quality".
He added: "Realising our ambition will take sustained investment in cycling and walking infrastructure.
"That's why we have committed over £300m to support cycling and walking over this Parliament and this will increase further when spending on enhancing and maintaining existing infrastructure is taken into account."
But British Cycling and CTC, the national cycling charity, have called for the objectives and funding proposals in the draft strategy to be strengthened.
They point to the parliamentary Get Britain Cycling report, which called for investment in cycling of at least £10 per person annually, rising to £20, in order to boost cycle use to 10% of trips by 2025, and to 25% by 2050.
The draft Cycling and Walking Investment Strategy provides central government funding of £300m over the period 2015-2020, amounting to £1.39 per person outside London, the campaigners said.
Chris Boardman, the 1992 individual pursuit Olympic champion and policy adviser for British Cycling, said "far more ambition" was needed if Britain was to create a cycling and walking culture to rival countries like Denmark and Holland.
Mr Boardman said: "The truth is that without sustained funding, this strategy won't be worth the paper it's written on. We know that when faced with other priorities like road maintenance, saving bus routes and new housing developments, cycling and walking will be put at the bottom of most councils' to-do lists."
The DfT said it would issue guidance to local bodies on developing local plans when the final strategy is published.
A new independent expert committee will be established by October 2016 to advise on the strategy and its implementation, it added.
The International Cricket Council will not send umpires to Pakistan to officiate in their upcoming limited-overs series against Zimbabwe because of security concerns.
[NEXT_CONCEPT]
The government has unveiled proposals to encourage people to cycle and walk more in England.