Files from third-party ROM sites like Romslab are frequently flagged by users for potential malware. If the archive contains an .exe file instead of an .nsp once extracted, it is almost certainly a virus.
To use this file, you would need a modified Switch running custom firmware (CFW). Connecting to official Nintendo servers while running such software or pirated games often leads to a permanent ban from the eShop and online play.
Before opening any downloaded files, it is highly recommended to upload the download link or the file itself to VirusTotal to scan it against multiple antivirus engines. Technical & Legal Risks
This is a compressed archive containing an NSP file, which is the standard format for digital Nintendo Switch games.