A copy of the book “Synopsis architecture civilis eclecticae” written by Johann Jacob Schübler can be found in the ETH Bibliothek in Zurich.
Adress: ETH Bibliothek Zürich, Rämistrasse 101, 8092 Zürich
The book is available digitally on different platforms:
https://www.e-rara.ch/doi/10.3931/e-rara-5305
https://reader.digitale-sammlungen.de/de/fs1/object/display/bsb11020708_00001.html
https://digi.ub.uni-heidelberg.de/diglit/schuebler1732bd1/0001