If the receiver declares that such goods are for authorised operations as per SEZ Rules, then on submission from your side you can make supply without charging IGST.
No you cannot collect GST on supply made to SeZ units . You have 2 options .1. File lut online on portal & not Required to charges IGST on bill (Export against Lut) or 2. You need to Charge IGST on bill & can claim refund for the same by filing RFD 01.