Difference between ISO EN 17025 and ISO IEC 17025

There is no difference, although reference to ISO/ EN 17025 or ISO EN 17025 is not strictly correct. ISO standards use the numbering format: "ISO nnnnn:yyyy: Title" where the standard number is "nnnnn", year published "yyyy” and the description of the subject is the “Title”. When jointly published with the International Electrotechnical Commission (IEC), as with ISO 17025; the numbering is ISO/IEC 17025:2017

National or regional standardization bodies may publish an equivalent version of the International Standard. An example is UNE EN ISO/IEC 17025:2017 General requirements for the competence of testing and calibration laboratories, where UNE is the legally authorised standardisation organisation in Spain. In some cases the year will be later than the ISO published year, where the year is the publication year for the regional or national standard. An example is AS ISO/IEC 17025:2018, published by Standards Australia in 2018.