/**
 * Convert a zoned ISO 8601 datetime string to a plain datetime string.
 *
 * - Extracts the local date-time components without timezone info.
 * - Validation is performed on the input.
 *
 * @param value zoned ISO 8601 datetime string
 * @returns plain datetime string or "" on invalid input
 *
 * @example convertZonedToPlainDateTime("2024-02-29T14:30:45.123-05:00[America/New_York]") // "2024-02-29T14:30:45.123"
 * @example convertZonedToPlainDateTime("invalid") // ""
 */
export declare function convertZonedToPlainDateTime(value: string): string;