Zieher is covered in the TPA site and German Wikipedia. Printing was mainly done in Leipzig. Most of the cards seem bear the firm's name rather than the pictorial logo.
The logo which is on the first example card appears on other early cards which have, as here, a local publsher's name; so Zieher was presumably the printer of these cards.
EKM is a logo which appears together with Ottmar's on illustrations/cartoons of beer drinking in Munich. The example is in a stein but there are other forms, eg in a shield. Maybe this is an illustrator's mark or it could be Emil Kohn Munich qv.
Ottmar Zieher was one of the Munich companies awarded the right to produce official postcardsof the Munich Exhibition of 1908.
The stamp cards. I can't find a reference on these, there must be one, but here are some notes sent by an unnamed ebay dealer in answer to a question posed on stampworld:
Zieher published four series of (stamp) cards with the first being by far the most extensive. In the first series there were stamp cards for 81 countries. In the first series Zieher tried to number serially the designs used for each country. The number on the face of most card is located at the top left, however seven are at the top right and six are at the top center. In the numerical series between No.1 and No. 114 are blanks where no country is designated, In addition there are a few cards without any assigned number, these being Belgium, United States and Kiachau. In the first series there are four basic types. Type 1 Outer border of lines and a framed rectangular message area. Type 2 Outer border of lines and an open message area. Type 3 Outer border of stripes and an open message area. Type 4 Outer border of stripes, open message area and a map added at lower right.
I don't know why the example card has a franked (real) stamp but no address. Maybe the message explains this.