could you please be more detailed with your query such as giving a scenario

One of The Company In DWC Selling Material in Same Freezone , So Custom Department Issue Transit Declartion Invoice, Kindly Explain In which Scienario Transit Document Issue by Custom Department

For sale of goods within a Free Zone the declaration issued by Customs is a Free Zone transit declaration. As a supplier all you need to ensure is whether the sale is subject to conditions laid down under Art 51 of ER where the transfer of material is within a Designated Zone (not necessarily a Free Zone) to asses the VAT implication.

In The Transit Invoice One of our TaxAdvisior Told me To ask letter from Supplier That He will not Resale that goods in UAE

i dont see a reason why they want a letter from Supplier to that effect. A letter from your Customer stating the goods purchased from you are not meant from for consumption where you sale is taking place in a Designated Zone is understandable since it is in accordance with exception granted tot supply of goods within a DZ. Dont understand the logic of the tax advisor