Zen is part of Buddhism. Both share an understanding of the Noble Eightfold Path, which starts with Right View:
AN2.126:1.1: “There are two conditions for the arising of right view. What two? The words of another and proper attention. These are the two conditions for the arising of right view.”
Teachers give us "the words of another". Without a teacher nearby, you can study the Early Buddhist Texts (EBTs) that inform all of Buddhism, including Zen. The EBTs are "words of another", in other words, they are the words of the Buddha and his immediate disciples. The EBTs also provide practice instructions that apply to zazen:
SN47.40:1.1: “Mendicants, I will teach you mindfulness meditation, the development of mindfulness meditation, and the practice that leads to the development of mindfulness meditation. Listen …
Zazen and Satipaṭṭhāna start with mindfulness of the body. When we sit, we observe our breath, not controlling it, simply observing it. A simple count suffices. I've been doing that for decades, and it still matters.
Zazen is traditionally done while sitting. However, one can meditate sitting, standing, walking or lying down, etc:
AN11.12:5.16: When they’re joyful, rapture springs up. When the mind is full of rapture, the body becomes tranquil. When the body is tranquil, they feel bliss. And when they’re blissful, the mind becomes immersed in samādhi. You should develop this recollection of the deities while walking, standing, sitting, lying down, while working, and while at home with your children.”
As you study and practice, you will want to discuss with others. If a Sangha is not readily available, you can reach out to others online just as you have done. It is not ideal, but it is available. As our practice deepens, spiritual companions invariably cross paths with us. Talk with them. Befriend them.
Zen is known for its koans. Although effective, they are of most value with greater context. Without such context, koans can inaccessibly perplexing. Many Zen texts provide great context, but I personally value the EBTs themselves as the authoritative context. In the light of the EBTs, one can really dig into the koans and understand the wonder of the Zen canon.
Zen and the EBTs have become the heart of my practice. May your own journey bring happiness to yourself and others.