If the work described in any Conditional Certificate of Zoning Compliance has not begun within 120 days of its issuance, the Certificate shall expire and it shall be canceled by the Zoning Administrator. Written notice of such cancellation shall be given to the applicant. If the work described in any Conditional Certificate of Zoning Compliance has not been substantially completed within two years of its issuance, the Certificate shall expire and it shall be canceled by the Zoning Administrator. Written notice of such cancellation shall be given to the applicant, together with notice that further work as described in the canceled Certificate shall not proceed unless and until a new Certificate has been obtained.