I haven’t been able to find a good table on Google images for the declension of dieser so I thought I’d make one. Here is both a copiable text one and an image with colour coding. The declension is the same whether dieser is used as a pronoun or a determiner.
Masculine | Feminine | Neuter | Plural | |
Nominative | dieser | diese | dieses | diese |
Accusative | diesen | diese | dieses | diese |
Genitive | dieses | dieser | dieses | dieser |
Dative | diesem | dieser | diesem | diesen |