400ZR and 400ZR+ are optical transceiver standards designed for high-speed, long-distance data transmission in optical networks. These standards are often associated with coherent optical communication for data center interconnects and wide-area networking. Please note that developments in standards and technologies may have occurred since my last update.  

Here are the key points differentiating 400ZR and 400ZR+:

1. 400ZR:

• Standardization: 400ZR is a standardized optical transceiver solution defined by the Optical Internetworking Forum (OIF). The OIF has specifications for 400ZR, outlining the requirements for interoperability and compliance.

• Data Rate: 400ZR is designed for a data rate of 400 Gbps (Gigabits per second).

• Distance: 400ZR is optimized for shorter-distance data center interconnects, typically targeting reaches of up to 120 km (kilometers) without the need for regeneration.

2. 400ZR+:

• As of my last knowledge update, there isn't a widely recognized standard or specification specifically named "400ZR+." The designation "400ZR+" may refer to an enhanced or extended version of the 400ZR standard or could be associated with advancements beyond the initial 400ZR specification.

• It's important to note that the "+" symbol in technology terms often signifies an improved or enhanced version. The specific features and enhancements associated with "400ZR+" would depend on the developments and standards set by relevant industry organizations or manufacturers.