ESI - Company is located in a Non Implemented zone but some of the workers are working in an implemented zone

Our Company is located in a Non- Implemented zone and we are not having ESI code. But our some of the workers are working in an implemented zone as a contractor in Principal company. Principal Company is asking us to Register ESI for the workers at their site. Is it Possible.
But we have WC Policy for the workers

Dear Friend,
If your company having 10 or more employees then need to apply for the ESIC code and WC is different act which could not be compile with ESIC benefits.