Supplies made overseas and to Special Economic Zones (SEZs) or SEZ Developers come under the zero-rated supplies. This supply attracts a GST of 0%. For such supplies, ITC can be claimed.
If the final output is Nil rated then ITC cannot be claimed. This article about ITC will solve all your doubts about ITC. https://irisgst.com/all-about-input-tax-credit-itc-how-to-claim-input-tax-credit/