A Kavacha is nothing but a Stotra having a peculiar feature.
Budha Kavacham (found in Brahma Vaivarta Purana) starts as follows:
Asya Budha kavacha stotra maha manthrasya
For the chant called Armour for Budha (mercury)
The sage is Sage Kasyapa
Meter is Anushtup
God is Budha (mercury)
Budha Preethyarthe Jape ...
The one you are reading is devi kavacham/durga kavacham,
https://sanskritdocuments.org/doc_devii/dkavach.html which is found in markandeya purana. Shree Durga Kavacham/Devyakavacham is a part of Durga Saptshati / Devi Mahatmya.
The one you found is from kubjikatantra (https://sanskritdocuments.org/doc_devii/durgAkavach.html). So what you are reading is ...
The concept of Trimūrti in specific-explicit reference to Brahmā, Viṣṇu, & Maheśa (Śhiva) is not stated explicitly in the Ṛg-Veda, i.e., the three deities which are discussed together as an "equivalent-triad" in detail, in the Paurāṇika-literature, are not discussed together as the tri-devas of the Trimūrti godhead, in any major Ṛg-Vedic ...
Not only Brahma, Vishnu, Shiva, all the deities in vedas are names of same Parabrahma.
Rigveda 1:164:46. They call him Indra, Mitra, Varuna, Agni, and he is heavenly nobly-winged Garutman. To what is One, sages give many a title they call it Agni, Yama, Matarisvan.
The same thing is said in other vedas.
Yajurveda 32:1. AGNI is That; the Sun is That; Vâyu ...